Table of Contents

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Form 10-K

Commission File Number: 001-33723

Main Street Capital Corporation
(Exact name of registrant as specified in its charter)

(713) 350-6000
(Registrant's telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

       Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes o    No þ

       Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    Yes o    No þ

       Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes þ    No o

       Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes o    No o

       Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.    þo

       Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act.

       Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes o    No þ

       The aggregate market value of the registrant's common stock held by non-affiliates of the registrant as of June 30, 2011,29, 2012, was approximately $439.3$683.5 million based upon the last sale price for the registrant's common stock on that date.

       The number of outstanding common shares of the registrant as of March 7, 20122013 was 26,966,752.34,744,667.

DOCUMENTS INCORPORATED BY REFERENCE

       Portions of the registrants' definitive Proxy Statement for its 20122013 Annual Meeting of Stockholders, to be filed with the Securities and Exchange Commission, are incorporated by reference in this Annual Report on Form 10-K in response to Part III.

Table of Contents

TABLE OF CONTENTS

Table of Contents

CAUTIONARY STATEMENT CONCERNING FORWARD LOOKING STATEMENTS

       This Annual Report on Form 10-K contains forward-looking statements regarding the plans and objectives of management for future operations. Any such forward-looking statements may involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from future results, performance or achievements expressed or implied by any forward-looking statements. Forward-lookingForward- looking statements, which involve assumptions and describe our future plans, strategies and expectations, are generally identifiable by use of the words "may," "will," "should," "expect," "anticipate," "estimate," "believe," "intend" or "project" or the negative of these words or other variations on these words or comparable terminology. These forward-looking statements are based on assumptions that may be incorrect, and we cannot assure you that the projections included in these forward-looking statements will come to pass. Our actual results could differ materially from those expressed or implied by the forward-looking statements as a result of various factors, including the factors discussed in Item 1A entitled "Risk Factors" in Part I of this Annual Report on Form 10-K and elsewhere in this Annual Report on Form 10-K. Other factors that could cause actual results to differ materially include changes in the economy and future changes in laws or regulations and conditions in our operating areas.

       We have based the forward-looking statements included in this Annual Report on Form 10-K on information available to us on the date of this Annual Report on Form 10-K, and we assume no obligation to update any such forward-looking statements, unless we are required to do so by applicable law. However, you are advised to consult any additional disclosures that we may make directly to you or through reports that we in the future may file with the SEC, including subsequent annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K.

PART I

Item 1.    Business

ORGANIZATION

       Main Street Capital Corporation ("MSCC") was formed on March 9, 2007 for the purpose of (i) acquiring 100% of the equity interests of Main Street Mezzanine Fund, LP ("MSMF") and its general partner, Main Street Mezzanine Management, LLC ("MSMF GP"), (ii) acquiring 100% of the equity interests of Main Street Capital Partners, LLC (the "Investment Manager"), (iii) raising capital in an initial public offering, which was completed in October 2007 (the "IPO"), and (iv) thereafter operating as an internally managed business development company ("BDC") under the Investment Company Act of 1940, as amended (the "1940 Act"). MSMF is licensed as a Small Business Investment Company ("SBIC") by the United States Small Business Administration ("SBA") and the Investment Manager acts as MSMF's manager and investment adviser. Because the Investment Manager, which employs all of the executive officers and other employees of MSCC, is wholly owned by us, we do not pay any external investment advisory fees, but instead we incur the operating costs associated with employing investment and portfolio management professionals through the Investment Manager. The IPO and related transactions discussed above were consummated in October 2007 and are collectively termed the "Formation Transactions."

       On January 7, 2010, MSCC consummated transactions (the "Exchange Offer") to exchange 1,239,695 shares of its common stock for approximately 88% of the total dollar value of the limited partner interests in Main Street Capital II, LP ("MSC II") and, together with MSMF, the "Funds"). Pursuant to the terms of the Exchange Offer, 100% of the membership interests in the general partner of MSC II, Main Street Capital II GP, LLC ("MSC II GP"), were also transferred to MSCC for no consideration. MSC II commenced operations in January 2006, is an investment fund that operates as an SBIC and is also managed by the Investment Manager. The Exchange Offer and related transactions, includingDuring the transferfirst quarter of 2012, MSCC exchanged 229,634 shares of its common stock to acquire all of the MSC II GP interests, are collectively termed the "Exchange Offer Transactions" (see Note J to the consolidated financial statements). As of December 31, 2011, an approximately 12%remaining minority ownership in the total dollar value of the MSC II limited partnership interests, remained outstanding, including approximately 5% owned by affiliates of MSCC (the "Final MSC II Exchange"). After the completion of the Final MSC II Exchange, MSCC owns 100% of MSC II. The Exchange Offer and

Table of Contents

affiliates of MSCC. On February 14, 2012, MSCC obtained exemptive relief fromrelated transactions, including the SEC to permit it to acquire the approximately 5% ownership in the total dollar valuetransfer of the MSC II limited partnershipGP interests held by affiliates of MSCC usingand the same valuation formula utilized in the Exchange Offer. On February 17, 2012, MSCC acquired a total of approximately 8.5% ownership in the total dollar value of theFinal MSC II limited partnership interests not owned by MSCC, includingExchange, are collectively termed the approximately 5% held by affiliates of MSCC, in exchange for 170,203 shares of its common stock. After the acquisition of these additional MSC II limited partnership interests on February 17, 2012, an approximately 3.0% minority ownership in the total dollar value of the MSC II limited partnership interests remained outstanding."Exchange Offer Transactions."

       MSCC has elected to be treated for federal income tax purposes as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). As a result, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that it distributes to its stockholders as dividends.

       MSCC has direct orand indirect wholly owned subsidiaries that have elected to be taxable entities (the "Taxable Subsidiaries"). The primary purpose of these entities is to hold certain investments that generate "pass through" income for tax purposes. The Taxable Subsidiaries are each taxed at their normal corporate tax rates based on their taxable income.

       Unless otherwise noted or the context otherwise indicates, the terms "we," "us," "our" and "Main Street" refer to MSCC and its consolidated subsidiaries, includingwhich include the Funds and the Taxable Subsidiaries.

       The following diagram depicts Main Street's organizational structure:

*

Each of the Taxable Subsidiaries is directly or indirectly wholly-owned by MSCC.

CORPORATE INFORMATION

       Our principal executive offices are located at 1300 Post Oak Boulevard, Suite 800, Houston, Texas 77056. We maintain a Web site on the Internet atwww.mainstcapital.com. We make available free of charge on our Web site our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and all amendments to those reports as soon as reasonably practicable after such material is electronically filed with or furnished to the Securities and Exchange Commission. You may read and copy any materials we file with the SEC at the SEC's Public Reference Room at 100 F Street, NE, Washington, DC 20549. You may obtain information regarding the Public Reference Room by calling the SEC at 1-800-SEC-0330. Information contained on our Web site is not incorporated by reference into this Annual Report on Form 10-K, and you should not consider that information to be part of this Annual Report on Form 10-K.

OVERVIEW OF OUR BUSINESS

       We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies which we generally define asand debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies with annual revenues between $10 million and $100 million that operate in diverse industries.industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt instruments,investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States. Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt

Table of Contents

investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million. Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM and Middle Market portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

       We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the lower middle marketLMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing solutions,options, or a "one stop" financing.financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

Table       As of Contents

December 31, 2012, we had debt and equity investments in 59 LMM portfolio companies with an aggregate fair value of approximately $510.3 million, a total cost basis of approximately $408.0 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.2%. As of December 31, 2012, approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 94% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 90% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 32%. As of December 31, 2011, we had debt and equity investments in 54 LMM portfolio companies with an aggregate fair value of approximately $429.1$415.7 million, a total cost basis of approximately $362.4$349.0 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.8%. Approximately 75%As of ourDecember 31, 2011, approximately 74% of Main Street's total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies as of December 31, 2011.companies. At December 31, 2011, we had equity ownership in approximately 94% of ourits LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 34%. The weighted average annual yields were computed using the effective interest rates for all debt investments as of December 31, 2012 and 2011, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments and any debt investments on non-accrual status.

       In addition to our LMM investment strategy, we opportunistically pursue investments in privately placed debt securities.Middle Market companies. Our private placement investmentMiddle Market portfolio investments primarily consistsconsist of direct or secondary private placements of interest bearinginvestments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our investmentLMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and five years.

       As of December 31, 2011,2012, we had privately placedMiddle Market portfolio investments in 2785 companies collectively totaling approximately $132.9$390.0 million in fair value with a total cost basis of approximately $133.4$385.5 million. The weighted average revenuesannual revenue for the 27 privately placed85 Middle Market portfolio company investments werewas approximately $367$513.5 million as of December 31, 2011. Our privately placed2012. As of December 31, 2012, almost all of our Middle

Table of Contents

Market portfolio investments are primarilywere in the form of debt investments and 69%approximately 92% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our privately placedMiddle Market portfolio debt investments was approximately 10.6%8.8% as of December 31, 2012. As of December 31, 2011, we had Middle Market portfolio investments in 57 companies collectively totaling approximately $226.5 million in fair value with a total cost basis of approximately $228.9 million. The weighted average annual revenue for the 57 Middle Market portfolio company investments was approximately $472.6 million as of December 31, 2011. As of December 31, 2011, almost all of our Middle Market portfolio investments were in the form of debt investments and approximately 82% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 9.5% as of December 31, 2011. The weighted average annual yields were computed using the effective interest rates for all debt investments as of December 31, 2012 and 2011, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments.

       As of December 31, 2012, we had Other Portfolio investments in 3 companies collectively totaling approximately $24.1 million in fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our investment portfolio at fair value as of December 31, 2012. As of December 31, 2011, we had Other Portfolio investments in 3 companies collectively totaling approximately $14.1 million in both fair value and cost basis and which comprised 2.1% of our investment portfolio at fair value as of December 31, 2011.

       Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes (see "— Regulation""Regulation"). An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF is a wholly owned subsidiary of MSCC and MSC II is a majorityare both wholly owned subsidiarysubsidiaries of MSCC.

       The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

RECENT DEVELOPMENTS

       On January 5, 2012, Main Street fully exited       MSCC and its debt and equity investments in Currie Acquisitions, LLC ("Currie"). Main Street completedconsolidated subsidiaries are internally managed by the exitInvestment Manager, a wholly owned subsidiary of its debt and equity investments in Currie as part of a buyout of Currie by Accell Group, a Netherlands-based international conglomerate. Main Street exited its debt investment for the full principal amount of approximately $4.8 million and recognized a realized loss of approximately $1.2 million on its equity investment.

       On February 17, 2012, MSCC, acquired a total of approximately 8.5%which employs all of the total dollar valueexecutive officers and other employees of Main Street. Because the MSC II limited partnership interests notInvestment Manager is wholly owned by MSCC, including the approximately 5% held by affiliates of MSCC, in exchange for 170,203 shares of its common stock. Subsequent to the acquisition, an approximately 3.0% minority ownership in the total dollar value of the MSC II limited partnership interests remained outstanding.

       On February 29, 2012, Main Street completeddoes not pay any external investment advisory fees, but instead incurs the exit of its debtoperating costs associated with employing investment and portfolio management professionals through the Investment Manager. We believe that our internally managed structure provides us with a portionbeneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio. For the year ended December 31, 2012, the ratio of its equity investments in Drilling Info,our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.8%, compared to 2.2% for the year ended December 31, 2011.

       In addition, during May 2012, MSCC and the Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP, which is the investment advisor to HMS Income Fund, Inc., ("Drilling Info"), as part of an equity investmenta non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in Drilling Info by a group of leading private equity investment firms focused on the global software, Internet and data-servicesJune

Table of Contents

industries. As part2012, to provide certain investment advisory services to HMS Adviser, LP. MSCC is initially providing such investment advisory services to HMS Adviser, LP, but we ultimately intend that the Investment Manager will provide such services because the fees we receive from such arrangement could otherwise have negative consequences on MSCC's ability to meet the source-of-income requirement necessary for MSCC to maintain its RIC tax treatment. We will need to obtain certain relief from the SEC before the Investment Manager is permitted to provide these services to HMS Adviser, LP, which we are seeking, but there can be no assurance that we will obtain such relief.

RECENT DEVELOPMENTS

       During January 2013, we invested $40.5 million of capital in Quality Lease and Rental Holdings, LLC, the exit,parent company of Quality Lease Service, LLC and Quality Lease Rental Service, LLC (together, "Quality"). Main Street realizedStreet's investment consists of $38 million in senior, secured term debt in Quality and a gain$2.5 million direct equity investment in Quality's parent holding company. Founded in 1989, Quality is headquartered in El Campo, Texas and provides drill site services and equipment rentals to the upstream oil and gas industry. Quality provides high quality, custom built mobile housing units to be used at the well site during drilling and completion operations. Quality also provides a variety of approximately $9.2 million onother services at the sale of its equity warrant participationwell site, including pad, pit, and received the full repayment of the principal amount of $8.0 million on its debt investment.road construction, pipeline and flow line equipment installation, equipment rental and heavy hauling.

       OnDuring March 6, 2012, Main Street2013, we declared regular monthly dividends for the second quarter of 2012 of $0.14$0.155 per share for each of April, May and June 2012, or2013. These regular monthly dividends equal a total of $0.42$0.465 per share.share for the second quarter of 2013. The second quarter 20122013 regular monthly dividends represent a 7.7%10.7% increase from the dividends declared for the second quarter of 2011 and a 3.7% increase compared to the first quarter of 2012. Including the dividends declared for the second quarter of 2012, Main Street2013, we will have paid $7.14$9.29 per share in cumulative dividends since itsour October 2007 initial public offering.

BUSINESS STRATEGIES

       Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and realizing capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. We have adopted the following business strategies to achieve our investment objective:

•

DeliveringDeliver Customized Financing Solutions in the Lower Middle Market. We believe our ability to provide a broad range of customized financing solutions to LMM companies sets us apart from other capital providers that focus on providing a limited number of financing solutions. We offer to our LMM portfolio companies customized debt financing solutions with equity components that are tailored to the facts and circumstances of each situation. Our ability to invest across a company's capital structure, from senior secured loans to subordinated debt to equity securities, allows us to offer our LMM portfolio companies a comprehensive suite of financing solutions,options, or a "one-stop" financing.financing solution.



•

FocusingFocus on Established Companies.We generally invest in companies with established market positions, experienced management teams and proven revenue streams. Those companies generally possess better risk-adjusted return profiles than newer companies that are building their management teams or are in the early stages of building a revenue base. We also believe that established companies in our targeted size range also generally provide opportunities for capital appreciation.



•

LeveragingLeverage the Skills and Experience of Our Investment Team.Our investment team has significant experience in lending to and investing in LMM and middle marketMiddle Market companies. The members of our investment team have broad investment backgrounds, with prior experience at private investment funds, investment banks and other financial services companies, and currently include eightsix certified public accountants and one chartered financial analysts.three Chartered Financial Analyst® (CFA) charter holders. The expertise of our investment team in analyzing, valuing, structuring, negotiating and closing transactions should provide us with competitive advantages by allowing us to consider customized financing solutions and non-traditional or complex structures for our portfolio companies.

Also, the reputation of our

Table of Contents

investment team has and should continue to enable us to generate additional revenue in the form of management and incentive fees in connection with us providing advisory services to other investment funds.

•

InvestingInvest Across Multiple Companies, Industries, Regions and End Markets.We seek to maintain a portfolio of investments that is appropriately balanced among various companies, industries, geographic regions and end markets. This portfolio balance is intended to mitigate the potential effects of negative economic events for particular companies, regions, industries and end markets.



•

CapitalizingCapitalize on Strong Transaction Sourcing Network. Our investment team seeks to leverage its extensive network of referral sources for portfolio company investments. We have developed a reputation in our marketplace as a responsive, efficient and reliable source of financing, which has created a growing stream of proprietary deal flow for us.



•

BenefitingBenefit from Lower, Fixed, Long-Term Cost of Capital. The SBIC licenses held by the Funds have allowed them to issue SBA-guaranteed debentures. SBA-guaranteed debentures carry long-term fixed rates that are generally lower than rates on comparable bank and other debt. Because lower cost SBA leverage is, and will continue to be, a significant part of our capital base through the Funds, our relative cost of debt capital should be lower than many of our competitors. In addition, the SBIC

Table of Contents

leverage that we receive through the Funds represents a stable, long-term component of our capital structure with proper matching of duration and cost compared to our LMM portfolio investments.

INVESTMENT CRITERIA

       Our investment team has identified the following investment criteria that it believes are important in evaluating prospective portfolio companies. Our investment team uses these criteria in evaluating investment opportunities. However, not all of these criteria have been, or will be, met in connection with each of our investments.

•

Proven Management Team with Meaningful Equity Stake. We look for operationally-oriented management with direct industry experience and a successful track record. In addition, we expect the management team of each LMM portfolio company to have meaningful equity ownership in the portfolio company to better align our respective economic interests. We believe management teams with these attributes are more likely to manage the companies in a manner that both protects our debt investment and enhances the value of our equity investment.



•

Established Companies with Positive Cash Flow. We seek to invest in established companies with sound historical financial performance. We typically focus on LMM companies that have historically generated EBITDA ("Earnings Before Interest, Taxes, Depreciation and Amortization") of $3 million to $20 million and commensurate levels of free cash flow. We also opportunistically pursue investments in privately placed debt securities inof Middle Market companies that are generally established companies with sound historical financial performance that are generally larger in size than LMM companies. We generally do not invest in start-up companies or companies with speculative business plans.



•

Defensible Competitive Advantages/Favorable Industry Position. We primarily focus on companies having competitive advantages in their respective markets and/or operating in industries with barriers to entry, which may help to protect their market position and profitability.



•

Exit Alternatives. We exit our debt investments primarily through the repayment of our investment from internally generated cash flow of the portfolio company and/or refinancing. In addition, we seek to invest in companies whose business models and expected future cash flows may provide alternate methods of repaying our investment, such as through a strategic acquisition by other industry participants or a recapitalization.

Table of Contents

PORTFOLIO INVESTMENTS

       Main Street's portfolio investments, as used herein, refers to all of Main Street's LMM portfolio investments, privately placedMiddle Market portfolio investments, Other Portfolio investments and its investment in the Investment Manager andbut excludes all marketableMarketable securities and idle funds investments. Main Street's LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies.companies based in the United States. Main Street's privately placedMiddle Market portfolio investments primarily consist of primarily debtdirect or secondary investments in middle market businessesinterest-bearing debt securities in companies based in the United States that are generally larger in size than the portfolio companies within theincluded in Main Street's LMM portfolio. Main Street's Other Portfolio investments primarily consist of investments which are not consistent with the typical profiles for our LMM and Middle Market portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

Debt Investments

       Historically, we have made LMM debt investments principally in the form of single tranche debt. Single tranche debt financing involves issuing one debt security that blends the risk and return profiles of both first lien secured and subordinated debt. We believe that single tranche debt is more appropriate for many LMM companies given their size in order to reduce structural complexity and potential conflicts among creditors.

       Our LMM debt investments generally have terms of three to seven years, with limited required amortization prior to maturity, and provide for monthly or quarterly payment of interest at fixed interest rates generally between 12% and 14% per annum, payable currently in cash. In some instances, we have provided

Table of Contents

floating interest rates for a portion of a single tranche debt security. In addition, certain LMM debt investments may have a form of interest that is not paid currently but is accrued and added to the loan balance and paid at maturity. We refer to this as payment-in-kind, or PIK, interest. We typically structure our LMM debt investments with the maximum seniority and collateral that we can reasonably obtain while seeking to achieve our total return target. In most cases, our LMM debt investment will be collateralized by a first priority lien on substantially all the assets of the portfolio company. As of December 31, 2011, 93%2012, 94% of our LMM debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies.

       In addition to seeking a senior lien position in the capital structure of our LMM portfolio companies, we seek to limit the downside potential of our LMM investments by negotiating covenants that are designed to protect our LMM investments while affording our portfolio companies as much flexibility in managing their businesses as is reasonable. Such restrictions may include affirmative and negative covenants, default penalties, lien protection, change of control or change of management provisions, key-man life insurance, guarantees, equity pledges, personal guaranties, where appropriate, and put rights. In addition, we typically seek board representation or observation rights in all of our LMM portfolio companies.

       While we will continue to focus our LMM investments primarily on single tranche debt investments, we also anticipate structuring some of our debt investments as mezzanine loans. We anticipate that these mezzanine loans will be primarily junior secured or unsecured, subordinated loans that provide for relatively high fixed interest rates payable currently in cash that will provide us with significant current interest income.income plus the additional opportunity for income and gains through PIK interest and equity warrants and other similar equity instruments issued in conjunction with these mezzanine loans. These loans typically will have interest-only payments in the early years, with amortization of principal deferred to the later years of the mezzanine loan term. Typically, our mezzanine loans will have maturities of three to five years. We will generally target fixed interest rates of 12% to 14%, payable currently in cash for our mezzanine loan investments with higher targeted total returns from equity warrants direct equity investments or PIK interest.

       In addition to our LMM debt investment strategy, we opportunistically pursue debt investments in privately placed debt securities. This private placement investmentMiddle Market companies. Our Middle Market portfolio investments primarily consistsconsist of direct or secondary private placementsinvestments in

Table of Contents

interest-bearing debt securities in companies based in the United States that are generally larger in size than the LMM companies included in our investmentLMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and typically have a term of between three and five years. The private placementdebt investments in our Middle Market portfolio have rights and protections that are similar to those in our LMM debt investments that are designed to protect our Middle Market debt investments, and which may include affirmative and negative covenants, default penalties, lien protection, change of control provisions, guarantees, and equity pledges. The Middle Market debt investments generally have floating interest rates at LIBOR plus a premium and subject to LIBOR floors and a term of five to seven years.floors. As of December 31, 2011,2012, almost all of our privately placedMiddle Market portfolio investments were primarily in the form of debt investments, allwith approximately 99% of which werethese investments at cost secured by portfolio company assets and with 69%approximately 92% of such debt investments at cost secured by first priority liens.

Warrants

       In connection with our LMM debt investments, we have historically received equity warrants to establish or increase our equity interest in the LMM portfolio company. Warrants we receive in connection with a LMM debt investment typically require only a nominal cost to exercise, and thus, as a LMM portfolio company appreciates in value, we may achieve additional investment return from this equity interest. We typically structure the warrants to provide provisions protecting our rights as a minority-interest holder, as well as secured or unsecured put rights, or rights to sell such securities back to the LMM portfolio company, upon the occurrence of specified events. In certain cases, we also may obtain registration rights in connection with these equity interests, which may include demand and "piggyback" registration rights.

Direct Equity Investments

       We also will seek to make direct equity investments in situations where it is appropriate to align our interests with key management and stockholders of our LMM portfolio companies, and to allow for some participation in the appreciation in the equity values of our LMM portfolio companies. We usually make our direct equity investments in connection with debt investments. In addition, we may have both equity warrants and direct equity positions in some of our LMM portfolio companies. We seek to maintain fully diluted equity positions in our LMM portfolio companies of 5% to 50%, and may have controlling equity interests in some instances. We

Table of Contents

have a value orientation toward our direct equity investments and have traditionally been able to purchase our equity investments at reasonable valuations.

INVESTMENT PROCESS

       Our investment committee is responsible for all aspects of our LMM investment process. The current members of our investment committee are Vincent D. Foster, our Chairman, President and Chief Executive Officer, Todd A. Reppert, our President,Executive Vice Chairman, and David Magdol, our Chief Investment Officer and Senior Managing Director.

       Our credit committee is responsible for all aspects of our private placementMiddle Market portfolio investment process. The current members of our credit committee are Messrs. Foster, and Reppert and Curtis Hartman, our Chief Credit Officer and Senior Managing Director.

       Our investment strategy involves a "team" approach, whereby potential transactions are screened by several members of our investment team before being presented to the investment committee or the credit committee, as applicable. Our investment committee and credit committee each meet on an as needed basis depending on transaction volume. We generally categorize our investment process into seven distinct stages:

Deal Generation/Origination

       Deal generation and origination is maximized through long-standing and extensive relationships with industry contacts, brokers, commercial and investment bankers, entrepreneurs, servicesservice providers such as lawyers, financial advisors, and accountants as well asand current and former portfolio companies and investors. Our investment team has focused its deal generation and origination efforts on LMM and middle marketMiddle Market companies. We have developed a reputation as a knowledgeable, reliable and active source of capital and assistance in this market.these markets.

Table of Contents

Screening

       During the screening process, if a transaction initially meets our investment criteria, we will perform preliminary due diligence, taking into consideration some or all of the following information:

•

a comprehensive financial model based on quantitative analysis of historical financial performance, projections and pro forma adjustments to determine the estimated internal rate of return;



•

a brief industry and market analysis;



•

direct industry expertise imported from other portfolio companies or investors;



•

preliminary qualitative analysis of the management team's competencies and backgrounds;



•

potential investment structures and pricing terms; and



•

regulatory compliance.

       Upon successful screening of a proposed LMM transaction, the investment team makes a recommendation to our investment committee. If our investment committee concurs with moving forward on the proposed LMM transaction, we typically issue a non-binding term sheet to the company. For privately placedMiddle Market portfolio investments, the initial term sheet is typically issued by the borrower, and is screened by the investment team which makes a recommendation to our credit committee.

Term Sheet

       For proposed LMM transactions, the non-binding term sheet will include the key economic terms based upon our analysis performed during the screening process as well as a proposed timeline and our qualitative expectation for the transaction. While the term sheet is non-binding, for LMM investments is non-binding we typically receive an expense deposit in order to move the transaction to the due diligence phase. Upon execution of a term sheet we begin our formal due diligence process.

Table of Contents

       For proposed private placementMiddle Market transactions, the internalinitial term sheet will include key economic terms and other conditions proposed by the borrower and its representatives and the proposed timeline for the investment, which are reviewed by our investment team to determine if such terms and conditions are in agreement with Main Street's investment objectives.

Due Diligence

       Due diligence on a proposed LMM investment is performed by a minimum of two of our investment professionals, whom we refer to collectively as the investment team, and certain external resources, who together conduct due diligence to understand the relationships among the prospective portfolio company's business plan, operations and financial performance. Our LMM due diligence review includes some or all of the following:

•

site visits with management and key personnel;



•

detailed review of historical and projected financial statements;



•

operational reviews and analysis;



•

interviews with customers and suppliers;



•

detailed evaluation of company management, including background checks;



•

review of material contracts;



•

in-depth industry, market, and strategy analysis;



•

regulatory compliance analysis; and



•

review by legal, environmental or other consultants, if applicable.

Table of Contents

       Due diligence on a proposed private placementMiddle Market investment is generally performed on materials and information obtained from certain external resources and assessed internally by a minimum of two of our investment professionals, who work to understand the relationships among the prospective portfolio company's business plan, operations and financial performance using the accumulated due diligence information. Our private placementMiddle Market due diligence review includes some or all of the following:

•

detailed review of historical and projected financial statements;



•

in-depth industry, market, operational and strategy analysis;



•

regulatory compliance analysis; and



•

detailed review of the company's management team and their capabilities.

       During the due diligence process, significant attention is given to sensitivity analyses and how the company might be expected to perform given downside, "base-case"base-case and upside scenarios. In certain cases, we may decide not to make an investment based on the results of the diligence process.

Document and Close

       Upon completion of a satisfactory due diligence review of a proposed LMM portfolio investment, the investment team presents the findings and a recommendation to our investment committee. The presentation contains information which can include, but is not limited to, the following:

•

company history and overview;



•

transaction overview, history and rationale, including an analysis of transaction strengths and risks;



•

analysis of key customers and suppliers and key contracts;



•

a working capital analysis;



•

an analysis of the company's business strategy;



•

a management and key equity investor background check and assessment;

Table of Contents

•

third-party accounting, legal, environmental or other due diligence findings;



•

investment structure and expected returns;



•

anticipated sources of repayment and potential exit strategies;



•

pro forma capitalization and ownership;



•

an analysis of historical financial results and key financial ratios;



•

sensitivities to management's financial projections;



•

regulatory compliance analysis findings; and



•

detailed reconciliations of historical to pro forma results.

       Upon completion of a satisfactory due diligence review of a proposed private placementMiddle Market portfolio investment, the investment team presents the findings and a recommendation to our credit committee. The presentation contains information which can include, but is not limited to, the following:

•

company history and overview;



•

transaction overview, history and rationale, including an analysis of transaction strengths and risks;



•

analysis of key customers and suppliers;



•

an analysis of the company's business strategy;



•

investment structure and expected returns;

may be subject to restrictions on resale. LMM investments and Other Portfolio investments generally have no established trading market while Middle Market securities generally have established markets that are not active. We determine in good faith the fair value of our portfolio investments pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. WeFor LMM investments, we review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For Middle Market portfolio debt and Other Portfolio debt investments, we primarily use observable inputs such as quoted prices in the valuation process. For Other Portfolio equity investments we generally value such investments based on the fair value of the portfolio company as determined by independent third parties, and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of the portfolio.

       For valuation purposes, control"control" LMM portfolio investments are composed of debt and equity and debt securities in companies for which we have a controlling interest in the portfolio company or have the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we determine the fair value of control investments using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the investments.various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate.generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

       For valuation purposes, non-control"non-control" LMM portfolio investments are composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company, or the ability to nominate a majority of the portfolio company's board of directors. Market quotations for our non-control LMM investments are generally not readily available.available for non-control LMM portfolio investments. For our non-control LMM investments, we use a combination of the market and income approaches to value our equity investments and the income approach to value our debt instruments. For non-controlinvestments similar to the approaches used for our control LMM debtportfolio investments, we determine the fair value primarilyand which includes using a yieldyield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of ana LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yieldyield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yieldyield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the face amount of the LMM debt security. A change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yieldyield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if ana LMM debt security is in workout status, we may consider other factors

Table of Contents

in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

       Pursuant to our internal valuation process and the requirements under the 1940 Act, we perform valuation procedures on our investments in each LMM portfolio company once a quarter. In addition to our internal valuation process, in arriving at estimates of fair value for our investments in LMM portfolio companies, we, among other things, consult with a nationally recognized independent advisor. The nationally recognized independent advisor is generally consulted relative to our investments in each LMM portfolio company at least once in every calendar year, and for our investments in new LMM portfolio companies, at least once in the twelve-month period subsequent to the initial investment. In certain instances, we may determine that it is not cost-effective, and as a result is not in our stockholders' best interest, to consult with the nationally recognized independent advisor on our investments in one or more LMM portfolio companies. Such instances include, but are not limited to, situations where the fair value of our investment in a LMM portfolio company is determined to be insignificant relative to the total investment portfolio. We consulted with our independent advisor in arriving at our determination of fair value on our investments in a total of 47 LMM portfolio companies for the year ended December 31, 2012, representing approximately 80% of the total LMM portfolio and investment in the affiliated Investment Manager at fair value as of December 31, 2012 and on a total of 42 portfolio companies, including 41 LMM portfolio companies and our affiliated Investment Manager, for the year ended December 31, 2011, representing approximately 81% of the total LMM portfolio and investment in the affiliated Investment Manager at fair value as of December 31, 2011.

For valuation purposes, all of our private placementMiddle Market portfolio investments are non-control investments and are composed of direct or secondary purchases of interest-bearing securities for which we do not have a

Table of Contents

controlling interest in the portfolio company, or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or other independent pricing. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach that is similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

       For valuation purposes, all of our Other Portfolio investments are non-control investments for which we generally do not have a controlling interest in the portfolio company, or the ability to nominate a majority of the portfolio company's board of directors. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. We value our Other Portfolio equity investments based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value of these investments through obtaining third party quotes or other independent pricing. To the extent observable inputs are not available for our Other Portfolio debt investments, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our non-control LMM portfolio debt investments.

       Due to the inherent uncertainty in the valuation process, our determination of fair value for our LMMportfolio investments may differ materially from the values that would have been used had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

       As described below, we undertake a multi-step valuation process each quarter in connection with determining the fair value of our investments, with our Board of Directors having final responsibility for

Table of Contents

overseeing, reviewing and approving, in good faith, our determination of the fair value of each individual investment.

•

Our quarterly valuation process will beginbegins with each LMM portfolio company or investment being initially valued by the investment team responsible for the portfolio investment;



•

The fair value determination for our Middle Market and Other Portfolio debt investments generally consists of observable inputs which are initially reviewed by the investment professionals responsible for the portfolio investment;



•

Preliminary valuation conclusions willare then be reviewed by and discussed with senior management, and the investment team considers and assesses, as appropriate, any changes that may be required to the preliminary valuations to address any comments provided by senior management;



•

AAs described above, a nationally recognized independent advisor engaged by the Board of Directors will performperforms certain mutually agreed limited procedures as described below, that we and the Board of Directors have identified and asked them to perform on a selection of our finalmanagement's LMM portfolio company valuation conclusions;



•

The fair value determination for our privately placed debt investments generally consists of observable inputs;



•

The Audit Committee of our Board of Directors will review the preliminaryreviews management's valuations, and the investment team willand senior management consider and assess, as appropriate, any changes that may be required to the preliminary valuationmanagement's valuations to address any comments provided by the Audit Committee; and



•

The Board of Directors will assessassesses the valuations and will ultimately approveapproves the fair value of each investment in our portfolio in good faith.

       As part of the internal valuation process, in determining fair value for LMM portfolio companies, Main Street, among other things, consults with a nationally recognized independent advisor. The nationally recognized independent advisor is generally consulted relative to each LMM portfolio investment at least once in every calendar year, and for new LMM portfolio companies, at least once in the twelve-month period subsequent to the initial investment. In certain instances, Main Street may determine that it is not cost-effective, and as a result is not in its stockholders' best interest, to consult with the nationally recognized independent advisor on one or more LMM portfolio companies. Such instances include, but are not limited to, situations where the fair value of Main Street's investment in a LMM portfolio company is determined to be insignificant relative to the total investment portfolio. Main Street consulted with its independent advisor in arriving at Main Street's determination of fair value on a total of 42 portfolio companies, including 41 LMM portfolio companies and our affiliated Investment Manager, for the year ended December 31, 2011, representing approximately 81% of the total LMM portfolio and investment in the affiliated Investment Manager at fair value as of December 31, 2011. The Board of Directors of Main Street has the final responsibility for reviewing and approving, in good faith, Main Street's determination of the fair value for the investments.

       Determination of fair value involves subjective judgments and estimates. The notes to our financial statements will refer to the uncertainty with respect to the possible effect of such valuations, and any change in such valuations, on our financial statements.

Table of Contents

COMPETITION

       We compete for investments with a number of investment funds (including private equity funds, mezzanine funds, BDCs, and SBICs), as well as traditional financial services companies such as commercial banks and other sources of financing. Many of the entities that compete with us have greater financial and managerial resources. We believe we are able to be competitive with these entities primarily on the basis of our focus toward the underserved lower middle market,LMM, the experience and contacts of our management team, our responsive and efficient investment analysis and decision-making processes, our comprehensive suite of customized financing solutions and the investment terms we offer.

       We believe that some of our competitors make senior secured loans, junior secured loans and subordinated debt investments with interest rates and returns that are comparable to or lower than the rates and returns that we target. Therefore, we do not seek to compete primarily on the interest rates and returns that we offer to potential portfolio companies. For additional information concerning the competitive risks we face, see "Risk Factors — Risks Related to Our Business and Structure — We may face increasing competition for investment opportunities."

EMPLOYEES

       As of December 31, 2011,2012, we had 2230 employees, each of whom was employed by the Investment Manager. These employees include investment and portfolio management professionals, operations professionals and administrative staff. As necessary, we will hire additional investment professionals and administrative personnel. All of our employees are located in our Houston, Texas office.

Table of Contents

REGULATION

Regulation as a Business Development Company

       We have elected to be regulated as a BDC under the 1940 Act. The 1940 Act contains prohibitions and restrictions relating to transactions between BDCs and their affiliates, principal underwriters and affiliates of those affiliates or underwriters. The 1940 Act requires that a majority of the members of the board of directors of a BDC be persons other than "interested persons," as that term is defined in the 1940 Act. In addition, the 1940 Act provides that we may not change the nature of our business so as to cease to be, or to withdraw our election as, a BDC unless approved by a majority of our outstanding voting securities.

       The 1940 Act defines "a majority of the outstanding voting securities" as the lesser of (i) 67% or more of the voting securities present at a meeting if the holders of more than 50% of our outstanding voting securities are present or represented by proxy or (ii) more than 50% of our outstanding voting securities.

Qualifying Assets

       Under the 1940 Act, a BDC may not acquire any asset other than assets of the type listed in Section 55(a) of the 1940 Act, which are referred to as qualifying assets, unless, at the time the acquisition is made, qualifying assets represent at least 70% of the company's total assets. The principal categories of qualifying assets relevant to our business are any of the following:

(1)

Securities purchased in transactions not involving any public offering from the issuer of such securities, which issuer (subject to certain limited exceptions) is an eligible portfolio company (as defined below), or from any person who is, or has been during the preceding 13 months, an affiliated person of an eligible portfolio company, or from any other person, subject to such rules as may be prescribed by the SEC.



(2)

Securities of any eligible portfolio company that we control.



(3)

Securities purchased in a private transaction from a U.S. issuer that is not an investment company or from an affiliated person of the issuer, or in transactions incident thereto, if the issuer is in bankruptcy and subject to reorganization or if the issuer, immediately prior to the purchase of its

Table of Contents

securities was unable to meet its obligations as they came due without material assistance other than conventional lending or financing arrangements.





(4)

Securities of an eligible portfolio company purchased from any person in a private transaction if there is no ready market for such securities and we already own 60% of the outstanding equity of the eligible portfolio company.



(5)

Securities received in exchange for or distributed on or with respect to securities described in (1) through (4) above, or pursuant to the exercise of warrants or rights relating to such securities.



(6)

Cash, cash equivalents, U.S. government securities or high-quality debt securities maturing in one year or less from the time of investment.

       In addition, a BDC must have been organized and have its principal place of business in the United States and must be operated for the purpose of making investments in the types of securities described in (1), (2) or (3) above.

       An eligible portfolio company is defined in the 1940 Act as any issuer which:

(a)

is organized under the laws of, and has its principal place of business in, the United States;



(b)

is not an investment company (other than a small business investment company wholly owned by the BDC) or a company that would be an investment company but for certain exclusions under the 1940 Act; and

Table of Contents

(c)

satisfies any of the following:



(i)

does not have any class of securities that is traded on a national securities exchange or has a class of securities listed on a national securities exchange but has an aggregate market value of outstanding voting and non-voting common equity of less than $250 million;



(ii)

is controlled by a BDC or a group of companies including a BDC and the BDC has an affiliated person who is a director of the eligible portfolio company; or



(iii)

is a small and solvent company having total assets of not more than $4 million and capital and surplus of not less than $2 million.

Managerial Assistance to Portfolio Companies

       In order to count portfolio securities as qualifying assets for the purpose of the 70% test, we must either control the issuer of the securities or must offer to make available to the issuer of the securities (other than small and solvent companies described above) significant managerial assistance; except that, where we purchase such securities in conjunction with one or more other persons acting together, one of the other persons in the group may make available such managerial assistance. Making available managerial assistance means, among other things, any arrangement whereby the BDC, through its directors, officers or employees, offers to provide, and, if accepted, does so provide, significant guidance and counsel concerning the management, operations or business objectives and policies of a portfolio company.

Temporary Investments

       Pending investment in "qualifying assets," as described above, our investments may consist of cash, cash equivalents, U.S. government securities and high quality debt securities maturing in one year or less from time of investment therein, so that 70% of our assets are qualifying assets.

Senior Securities

       We are permitted, under specified conditions, to issue multiple classes of debt and one class of stock senior to our common stock if our asset coverage, as defined in the 1940 Act, is at least equal to 200% of all debt and/or senior stock immediately after each such issuance. In addition, while any senior securities remain

Table of Contents

outstanding (other than senior securities representing indebtedness issued in consideration of a privately arranged loan which is not intended to be publicly distributed), we must make provisions to prohibit any distribution to our stockholders or the repurchase of such securities or shares unless we meet the applicable asset coverage ratios at the time of the distribution or repurchase. We may also borrow amounts up to 5% of the value of our total assets for temporary or emergency purposes without regard to asset coverage. For a discussion of the risks associated with leverage, see "Risk Factors — Risks Relating to Our Business and Structure," including, without limitation, "— Because we borrow money, the potential for gain or loss on amounts invested in us is magnified and may increase the risk of investing in us."

       In January 2008, we received an exemptive order from the SEC to exclude debt securities issued by MSMF and any other wholly owned subsidiaries of ours which operate as SBICs from the asset coverage requirements of the 1940 Act as applicable to Main Street. The exemptive order provides for the exclusion of all debt securities issued by the Funds, including the $220$225 million of currently outstanding debt related to itstheir participation in the SBIC program. This exemptive order provides us with expanded capacity and flexibility in obtaining future sources of capital for our investment and operational objectives.

Common Stock

       We are not generally able to issue and sell our common stock at a price below net asset value per share. We may, however, sell our common stock, warrants, options or rights to acquire our common stock, at a price below the current net asset value of the common stock if our board of directors determines that such sale is in our best interests and that of our stockholders, and our stockholders approve such sale. In any such case,

Table of Contents

the price at which our securities are to be issued and sold may not be less than a price which, in the determination of our board of directors, closely approximates the market value of such securities (less any distributing commission or discount). A proposal, approved by our stockholders at our June 20112012 annual meeting of stockholders, authorizes us to sell shares of our common stock below the then current net asset value per share of our common stock in one or more offerings for athe period ending on the earlier of (i) June 14, 2013, the one year ending on June 14, 2012.anniversary of our 2012 annual meeting of stockholders, and (ii) the date of our 2013 annual meeting of stockholders. We would need similar future approval from our stockholders to issue shares below the then current net asset value per share any time after the expiration of the current approval. We are seekingdo not currently expect to seek such approval for the next year at our 20122013 annual meeting of stockholders meeting to be held on June 14, 2012.because our common stock price per share has been trading significantly above the current net asset value per share of our common stock. On June 17, 2008, our stockholders approved another proposal that authorizes us to issue securities to subscribe to, convert to, or purchase shares of our common stock in one or more offerings. We may also make rights offerings to our stockholders at prices per share less than the net asset value per share, subject to applicable requirements of the 1940 Act. See "Risk Factors — Risks Relating to Our Business and Structure — Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock."

Code of Ethics

       We have adopted a code of ethics pursuant to Rule 17j-1 under the 1940 Act that establishes procedures for personal investments and restricts certain personal securities transactions. Personnel subject to the code may invest in securities for their personal investment accounts, including securities that may be purchased or held by us, so long as such investments are made in accordance with the code's requirements. You may read and copy the code of ethics at the SEC's Public Reference Room located at 100 F Street, NE, Washington, DC 20549. You may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. In addition, the code of ethics is available on the EDGAR Database on the SEC's website site athttp://www.sec.gov.

Proxy Voting Policies and Procedures

       We vote proxies relating to our portfolio securities in a manner in which we believe is consistent with the best interest of our stockholders. We review on a case-by-case basis each proposal submitted to a stockholder vote to determine its impact on the portfolio securities held by us. Although we generally vote against

Table of Contents

proposals that we expect would have a negative impact on our portfolio securities, we may vote for such a proposal if there exists compelling long-term reasons to do so.

       Our proxy voting decisions are made by the investment team which is responsible for monitoring each of our investments. To ensure that our vote is not the product of a conflict of interest, we require that: (i) anyone involved in the decision-making process to disclose to our chief compliance officer any potential conflict of which he or she is aware and any contact that he or she has had with any interested party regarding a proxy vote and (ii) employees involved in the decision making process or vote administration are prohibited from revealing how we intend to vote on a proposal in order to reduce any attempted influence from interested parties.

       Stockholders may obtain information, without charge, regarding how we voted proxies with respect to our portfolio securities by making a written request for proxy voting information to: Chief Compliance Officer, 1300 Post Oak Boulevard, Suite 800, Houston, Texas 77056.

Other 1940 Act Regulations

       We may also be prohibited under the 1940 Act from knowingly participating in certain transactions with our affiliates without the prior approval of our Board of Directors who are not interested persons and, in some cases, prior approval by the SEC.

Table of Contents

       We are required to provide and maintain a bond issued by a reputable fidelity insurance company to protect us against larceny and embezzlement. Furthermore, as a BDC, we are prohibited from protecting any director or officer against any liability to us or our stockholders arising from willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of such person's office.

       We are required to adopt and implement written policies and procedures reasonably designed to prevent violation of the federal securities laws, review these policies and procedures annually for their adequacy and the effectiveness of their implementation, and to designate a chief compliance officer to be responsible for administering the policies and procedures.

       We may be periodically examined by the SEC for compliance with the 1940 Act.

Small Business Investment Company Regulations

       Each of the Funds is licensed by the SBA to operate as a SBIC under Section 301(c) of the Small Business Investment Act of 1958. As a part of the Formation Transactions, MSMF became a wholly owned subsidiary of MSCC, and continues to hold its SBIC license. MSMF initially obtained its SBIC license in September 2002. As a part of the Exchange Offer Transactions, MSC II became a majority owned subsidiary of MSCC, and, as a part of the Final MSC II Exchange, MSC II became a wholly owned subsidiary of MSCC, and continues to hold its license. MSC II initiallythe license it obtained its SBIC license in January 2006.

       SBICs are designed to stimulate the flow of private equity capital to eligible small businesses. Under SBIC regulations, SBICs may make loans to eligible small businesses, invest in the equity securities of such businesses and provide them with consulting and advisory services. Each of the Funds has typically invested in secured debt, acquired warrants and/or made equity investments in qualifying small businesses.

       Under present SBIC regulations, eligible small businesses generally include businesses that (together with their affiliates) have a tangible net worth not exceeding $18 million and have average annual net income after federal income taxes not exceeding $6 million (average net income to be computed without benefit of any carryover loss) for the two most recent fiscal years. In addition, an SBIC must devote 25% of its investment activity to "smaller" concerns as defined by the SBA. A smaller concern generally includes businesses that have a tangible net worth not exceeding $6 million and have average annual net income after federal income taxes not exceeding $2 million (average net income to be computed without benefit of any net carryover loss) for the two most recent fiscal years. SBIC regulations also provide alternative size standard criteria to determine eligibility for designation as an eligible small business or smaller concern, which criteria depend on the primary industry in which the business is engaged and are based on such factors as the number of

Table of Contents

employees and gross revenue. However, once an SBIC has invested in a company, it may continue to make follow on investments in the company, regardless of the size of the portfolio company at the time of the follow on investment, up to the time of the portfolio company's initial public offering.

       The SBA prohibits an SBIC from providing funds to small businesses for certain purposes, such as relending and investment outside the United States, to businesses engaged in a few prohibited industries, and to certain "passive" (non-operating) companies. In addition, without prior SBA approval, an SBIC may not invest an amount equal to more than approximately 30% of the SBIC's regulatory capital in any one portfolio company and its affiliates.

       The SBA places certain limitations on the financing terms of investments by SBICs in portfolio companies (such as limiting the permissible interest rate on debt securities held by an SBIC in a portfolio company). Included in such limitations are SBA regulations which allow an SBIC to exercise control over a small business for a period of seven years from the date on which the SBIC initially acquires its control position. This control period may be extended for an additional period of time with the SBA's prior written approval.

       The SBA restricts the ability of an SBIC to lend money to any of its officers, directors and employees or to invest in affiliates thereof. The SBA also prohibits, without prior SBA approval, a "change of control" of an SBIC or transfers that would result in any person (or a group of persons acting in concert) owning 10% or

Table of Contents

more of a class of equity of a licensed SBIC. A "change of control" is any event which would result in the transfer of the power, direct or indirect, to direct the management and policies of an SBIC, whether through ownership, contractual arrangements or otherwise.

       An SBIC may generally have outstanding debentures guaranteed by the SBA in amounts up to twice the amount of the privately-raised funds of the SBIC(s). Debentures guaranteed by the SBA have a maturity of ten years, require semi-annual payments of interest, do not require any principal payments prior to maturity, and are not subject to prepayment penalties. As of December 31, 2011,2012, we, through the Funds, had issued $220$225 million of outstanding SBA-guaranteed debentures, which had an annual weighted average interest rate of approximately 5.1%4.7%.

       The American Recovery and Reinvestment Act of 2009 enacted in February 2009 (the "Stimulus Bill") contains several provisions applicable to SBIC funds, including the Funds. One of the key SBIC-related provisions included in the Stimulus Bill increased the maximum amount of combined SBIC leverage (or SBIC leverage cap) to $225 million for affiliated SBIC funds. The prior maximum amount of SBIC leverage available to affiliated SBIC funds was approximately $137 million. Since the increase in the SBIC leverage cap applies to affiliated SBIC funds, Main Street is required to allocate such increased borrowing capacity between the Funds.

       A proposed bill in the U.S. House of Representatives, the Small Business Investment Company Modernization Act of 2011, or House Bill 3219, would increase the total SBIC leverage capacity for affiliated SBIC funds from $225 million to $350 million. Another bill in the U.S. Senate, Senate Bill 2136, to increase the total SBIC leverage capacity for affiliated SBIC funds to $350 million, was recently introduced in the U.S. Senate and referred to the Committee on Small Business and Entrepreneurship. If either of these bills is enacted, Main Street's SBIC leverage capacity through the Funds would increase by an additional $125 million. While Main Street is positioned to benefit from the full passage of either bill, the ultimate form and likely outcome of such legislation or any similar legislation cannot be predicted.

       SBICs must invest idle funds that are not being used to make loans in investments permitted under SBIC regulations in the following limited types of securities: (i) direct obligations of, or obligations guaranteed as to principal and interest by, the United States government, which mature within 15 months from the date of the investment; (ii) repurchase agreements with federally insured institutions with a maturity of seven days or less (and the securities underlying the repurchase obligations must be direct obligations of or guaranteed by the federal government); (iii) certificates of deposit with a maturity of one year or less, issued by a federally insured institution; (iv) a deposit account in a federally insured institution that is subject to a withdrawal

Table of Contents

restriction of one year or less; (v) a checking account in a federally insured institution; or (vi) a reasonable petty cash fund.

       SBICs are periodically examined and audited by the SBA's staff to determine their compliance with SBIC regulations and are periodically required to file certain financial information and other documents with the SBA.

       Neither the SBA nor the U.S. government or any of its agencies or officers has approved any ownership interest to be issued by us or any obligation that we or any of our subsidiaries may incur.

Securities Exchange Act of 1934 and Sarbanes-Oxley Act Compliance

       We are subject to the reporting and disclosure requirements of the Securities Exchange Act of 1934 (the "Exchange Act"), including the filing of quarterly, annual and current reports, proxy statements and other required items. In addition, we are subject to the Sarbanes-Oxley Act of 2002, which imposes a wide variety of regulatory requirements on publicly-held companies and their insiders. For example:

•

pursuant to Rule 13a-14 of the Exchange Act, our Chief Executive Officer and Chief Financial Officer are required to certify the accuracy of the financial statements contained in our periodic reports;



•

pursuant to Item 307 of Regulation S-K, our periodic reports are required to disclose our conclusions about the effectiveness of our disclosure controls and procedures;



•

pursuant to Rule 13a-15 of the Exchange Act, our management is required to prepare a report regarding its assessment of our internal control over financial reporting, and our independent registered public accounting firm separately audits our internal control over financial reporting; and



•

pursuant to Item 308 of Regulation S-K and Rule 13a-15 of the Exchange Act, our periodic reports must disclose whether there were significant changes in our internal control over financial reporting or in other factors that could significantly affect these controls subsequent to the date of their evaluation, including any corrective actions with regard to significant deficiencies and material weaknesses.

The New York Stock Exchange Corporate Governance Regulations

       The New York Stock Exchange ("NYSE") has adopted corporate governance regulations that listed companies must comply with. We believe we are in compliance with such corporate governance listing standards. We intend to monitor our compliance with all future listing standards and to take all necessary actions to ensure that we stay in compliance.

Table of Contents

Investment Adviser Regulations

       We and the Investment Manager, which is wholly owned by us and employs all of our executive officers, investment professionals and other employees, are also subject to regulation under the Investment Advisers Act of 1940, as amended (the "Advisers Act"). The Advisers Act establishes, among other things, recordkeeping and reporting requirements, disclosure requirements, limitations on transactions between the adviser's account and an advisory client's account, limitations on transactions between the accounts of advisory clients, and general anti-fraud prohibitions. We and the Investment Manager will also be examined by the SEC from time to time for compliance with the Advisers Act.

Taxation as a Regulated Investment Company

       MSCC has elected to be treated for federal income tax purposes as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code (the "Code") commencing October 2, 2007. As a RIC, we generally do not have to pay corporate-levelcorporate level federal income taxes on any income that we distribute to our stockholders as dividends. To qualify as a RIC, we must, among other things, meet certain source-of-income and asset diversification requirements (as described below). In addition, in order to obtain RIC tax treatment, we must distribute to our stockholders, for each taxable year, at least 90% of our

Table of Contents

"investment "investment company taxable income," which is generally our net ordinary income plus the excess of realized net short-term capital gains over realized net long-term capital losses (the "Annual Distribution Requirement").

       For any taxable year in which we qualify as a RIC and satisfy the Annual Distribution Requirement, we will not be subject to federal income tax on the portion of our income or capital gains we distribute (or are deemed to distribute) to stockholders. We will be subject to U.S. federal income tax at the regular corporate rates on any income or capital gains not distributed (or deemed distributed) to our stockholders.

       We will be subject to a 4% nondeductible federal excise tax on certain undistributed income unless we distribute in a timely manner an amount at least equal to the sum of (1) 98% of our net ordinary income for each calendar year, (2) 98.2% of our capital gain net income for the one-year period ending December 31 in that calendar year and (3) any income recognized, but not distributed, in preceding years (the "Excise Tax Avoidance Requirement"). Dividends declared and paid by us in a year will generally differ from taxable income for that year as such dividends may include the distribution of current year taxable income, exclude amounts carried over into the following year, and include the distribution of prior year taxable income carried over into and distributed in the current year. For amounts we carry over into the following year, we will be required to pay the 4% excise tax based on 98% of our annual taxable income and 98.2% of our capital gain net income in excess of distributions for the year.

       In order to qualify as a RIC for federal income tax purposes, we must, among other things:

•

continue to qualify as a BDC under the 1940 Act at all times during each taxable year;



•

derive in each taxable year at least 90% of our gross income from dividends, interest, payments with respect to certain securities, loans, gains from the sale of stock or other securities, net income from certain "qualified publicly traded partnerships," or other income derived with respect to our business of investing in such stock or securities (the "90% Income Test"); and



•

diversify our holdings so that at the end of each quarter of the taxable year:



•

at least 50% of the value of our assets consists of cash, cash equivalents, U.S. Government securities, securities of other RICs, and other securities if such other securities of any one issuer do not represent more than 5% of the value of our assets or more than 10% of the outstanding voting securities of the issuer; and



•

no more than 25% of the value of our assets is invested in the securities, other than U.S. government securities or securities of other RICs, (i) of one issuer, (ii) of two or more issuers that are controlled, as determined under applicable Code rules, by us and that are engaged in the same

Table of Contents

or similar or related trades or businesses or (iii) of certain "qualified publicly traded partnerships" (collectively, the "Diversification Tests").

       In order to comply with the 90% Income Test, we formed the Taxable Subsidiaries as wholly owned taxable subsidiaries, for the primary purpose of permitting us to own equity interests in portfolio companies which are "pass through" entities for tax purposes. Absent the taxable status of the Taxable Subsidiaries, a portion of the gross income from such portfolio companies would flow directly to us for purposes of the 90% Income Test. To the extent such income did not consist of income derived from securities, such as dividends and interest, it could jeopardize our ability to qualify as a RIC and, therefore cause us to incur significant federal income taxes. The Taxable Subsidiaries are consolidated with Main Street for GAAP purposes, and the portfolio investments held by the Taxable Subsidiaries are included in our consolidated financial statements. The Taxable Subsidiaries are not consolidated with Main Street for income tax purposes and may generate income tax expense as a result of their ownership of the portfolio investments. This income tax expense, if any, is reflected in our Consolidated Statement of Operations.

       We may be required to recognize taxable income in circumstances in which we do not receive cash. For example, if we hold debt obligations that are treated under applicable tax rules as having original issue discount (such as debt instruments issued with warrants), and debt securities invested in at a discount to par, we must include in income each year a portion of

Table of Contents

the original issue discount that accrues over the life of the obligation, regardless of whether cash representing such income is received by us in the same taxable year. We may also have to include in income other amounts that we have not yet received in cash such as PIK interest, and deferred loan origination feescumulative dividends or amounts that are paid after origination of the loan or are paidreceived in non-cash compensation such as warrants or stock. Because any original issue discount or other amounts accrued will be included in our investment company taxable income for the year of accrual, we may be required to make a distribution to our stockholders in order to satisfy the Annual Distribution Requirement, even though we will not have received any corresponding cash amount.

       Although we do not presently expect to do so, we are authorized to borrow funds and to sell assets in order to satisfy distribution requirements. However, under the 1940 Act, we are not permitted to make distributions to our stockholders in certain circumstances while our debt obligations and other senior securities are outstanding unless certain "asset coverage" tests are met. See "— Regulation — Regulation as a Business Development Company — Senior Securities." Moreover, our ability to dispose of assets to meet our distribution requirements may be limited by (1) the illiquid nature of our portfolio and/or (2) other requirements relating to our status as a RIC, including the Diversification Tests. If we dispose of assets in order to meet the Annual Distribution Requirement or the Excise Tax Avoidance Requirement, we may make such dispositions at times that, from an investment standpoint, are not advantageous.

       Pursuant to a revenue procedure issuedWe may distribute taxable dividends that are payable in part in our stock. Under certain applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash or in shares of stock (at the stockholders election) would satisfy the Annual Distribution Requirement. The Internal Revenue Service orhas issued private rulings indicating that this rule will apply even where the IRS, the IRS has indicatedtotal amount of cash that it will treat distributions from certain publicly traded RICs (including business development companies) that are paid part in cash and part in stock as dividends that would satisfy the RIC's annual distribution requirements. In ordermay be distributed is limited to qualify for such treatment, the revenue procedure requires that at least 10%no more than 20% of the total distribution be paid in cash and that each stockholder have a right to elect to receive its entire distribution in cash. Ifdistribution. Under these rulings, if too many stockholders elect to receive their distributions in cash, each such stockholder electing to receive cash mustwould receive a proportionatepro rata share of the total cash to be distributed (although no stockholder electing toand would receive cash may receive less than 10%the remainder of such stockholder'stheir distribution in cash). This revenue procedure appliesshares of stock. Any distributions made consistent with these rulings that are payable in part in our stock, taxable stockholders receiving such dividends will be required to distributions declared oninclude the full amount of the dividend (whether received in cash, our stock, or before December 31, 2012,a combination thereof) as (i) ordinary income (including any qualified dividend income that, in the case of a noncorporate stockholder, may be eligible for the same reduced maximum tax rate applicable to long-term capital gains to the extent such distribution is properly reported by us as qualified dividend income and such stockholder satisfies certain minimum holding period requirements with respect to our stock) or (ii) long-term capital gain (to the extent such distribution is properly reported as a capital gain dividend), to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives in order to pay this

Table of Contents

tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

Failure to Qualify as a RIC

       If we fail to satisfy the 90% Income Test or the Diversification Tests for any taxable year, we may nevertheless continue to qualify as a RIC for such year if certain relief provisions are applicable (which may, among other things, require us to pay certain corporate-level federal taxes or to dispose of certain assets).

       If we were unable to qualify for treatment as a RIC and the foregoing relief provisions are not applicable, we would be subject to tax on all of our taxable income at regular corporate rates. We would not be able to deduct distributions to stockholders, nor would they be required to be made. Such distributions would be taxable to our stockholders and, provided certain holding period and other requirements were met, could qualify for treatment as "qualified dividend income" eligible for the 15% (or effective as of January 1, 2013, 20%) rate applicable to qualified dividends to the extent of our current and accumulated earnings and profits. Subject to certain limitations under the Code, corporate distributions would be eligible for the dividends-received deduction. Distributions in excess of our current and accumulated earnings and profits would be treated first as a return of capital to the extent of the stockholder's tax basis, and any remaining distributions would be treated as a capital gain. To requalify as a RIC in a subsequent taxable year, we would be required to satisfy the RIC qualification requirements for that year and dispose of any earnings and profits from any year in which we failed to qualify as a RIC. Subject to a limited exception applicable to RICs that qualified as such under Subchapter M of the Code for at least one year prior to disqualification and that requalify as a RIC no later than the second year following the nonqualifying year, we could be subject to tax on any unrealized net built-in gains in the assets held by us during the period in which we failed to qualify as a RIC that are recognized within the subsequent 10 years, endedunless we made a special election to pay corporate-level tax on or before December 31, 2011.such built-in gain at the time of our requalification as a RIC.

Table of Contents

Item 1A.    Risk Factors

       Investing in our common stocksecurities involves a number of significant risks. In addition to the other information contained in this Annual Report on Form 10-K, you should consider carefully the following information before making an investment in our common stock.securities. The risks set out below are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us might also impair our operations and performance. If any of the following events occur, our business, financial condition and results of operations could be materially and adversely affected. In such case, our net asset value and the trading price of our common stock or the value of our other securities could decline, and you may lose all or part of your investment.

RISKS RELATING TO ECONOMIC CONDITIONS

Deterioration in the economy and financial markets increases the likelihood of adverse effects on our financial position and results of operations. Such economic adversity could impair our portfolio companies' financial positions and operating results and affect the industries in which we invest, which could, in turn, harm our operating results.

       The broader economic fundamentals of the United States economy remain uncertain. Unemployment levels remain elevatedmixed, and other economic fundamentals remain depressed.unemployment remains elevated. In the event that the United States economic performanceeconomy contracts, it is likely that the financial results of small- to mid-sized companies, like those in which we invest, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt service requirements and an increase in defaults. Consequently, we can provide no assurance that the performance of certain of our portfolio companies will not be negatively impacted by economic cycles or other conditions, which could also have a negative impact on our future results.

       Although we have been able to secure access to additional liquidity, including our $235 million credit facility,through the Credit Facility, periodic follow-on equity offerings and the increase inleverage available leverage through the SBIC program, as part of the American Recovery and Reinvestment Act of 2009 enacted in the Stimulus Bill, the potential for volatility in the debt and equity capital markets provides no assurance that debt or equity capital will be available to us in the future on favorable terms, or at all. Further, if the price of our common stock falls below our net asset value per share, we will be limited in our ability to sell new shares if we do not have shareholder authorization to sell shares at a price below net asset value per share. We do not intend to seek such shareholder authorization at our 2013 stockholder meeting.

RISKS RELATING TO OUR BUSINESS AND STRUCTURE

Our investment portfolio is and will continue to be recorded at fair value, with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of fair value and, as a result, there is and will continue to be uncertainty as to the value of our portfolio investments.

       Under the 1940 Act, we are required to carry our portfolio investments at market value or, if there is no readily available market value, at fair value as determined by us with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of fair value. Typically, there is not a public market for the securities of the privately held LMM companies in which we have invested and will generally continue to invest. As a result, we value these securities quarterly at fair value based on inputs from management, a nationally recognized independent advisor (on a rotational basis) and our audit committee with the oversight, review and approval of our Board of Directors. In addition, the market for privately placedMiddle Market portfolio investments is generally not a liquid market, and therefore, we primarily use observable inputs to determine the fair value of these investments quarterly through obtaining third party quotes and other independent pricing, which are reviewed by our audit committee with the oversight, review and approval of our Board of Directors. See "Business — Determination of Net Asset Value and Portfolio Valuation Process" for a more detailed description of our valuation process.

Table of Contents

       The determination of fair value and consequently, the amount of unrealized gains and losses in our portfolio, are to a certain degree, subjective and dependent on a valuation process approved by our Board of Directors. Certain factors that may be considered in determining the fair value of our investments include

Table of Contents

external events, such as private mergers, sales and acquisitions involving comparable companies. Because such valuations, and particularly valuations of private securities and private companies, are inherently uncertain, may fluctuate over short periods of time and may be based on estimates, our determinations of fair value may differ materially from the values that would have been used if a ready market for these securities existed. Due to this uncertainty, our fair value determinations may cause our net asset value on a given date to materially understate or overstate the value that we may ultimately realize on one or more of our investments. As a result, investors purchasing our common stocksecurities based on an overstated net asset value would pay a higher price than the value of our investments might warrant. Conversely, investors selling sharesour securities during a period in which the net asset value understates the value of our investments willmay receive a lower price for their sharessecurities than the value of our investments might warrant.

Our financial condition and results of operations depends on our ability to effectively manage and deploy capital.

       Our ability to achieve our investment objective of maximizing our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company, depends on our ability to effectively manage and deploy capital, which depends, in turn, on our investment team's ability to identify, evaluate and monitor, and our ability to finance and invest in, companies that meet our investment criteria.

       Accomplishing our investment objective on a cost-effective basis is largely a function of our investment team's handling of the investment process, its ability to provide competent, attentive and efficient services and our access to investments offering acceptable terms. In addition to monitoring the performance of our existing investments, members of our investment team are also called upon, from time to time, to provide managerial assistance to some of our portfolio companies. These demands on their time may distract them or slow the rate of investment.

       Even if we are able to grow and build upon our investment operations, any failure to manage our growth effectively could have a material adverse effect on our business, financial condition, results of operations and prospects. The results of our operations will depend on many factors, including the availability of opportunities for investment, readily accessible short and long-term funding alternatives in the financial markets and economic conditions. Furthermore, if we cannot successfully operate our business or implement our investment policies and strategies as described herein, it could negatively impact our ability to pay dividends.

We may face increasing competition for investment opportunities.

       We compete for investments with other investment funds (including private equity funds, mezzanine funds, BDCs, and SBICs), as well as traditional financial services companies such as commercial banks and other sources of funding. Many of our competitors are substantially larger and have considerably greater financial, technical and marketing resources than we do. For example, some competitors may have a lower cost of capital and access to funding sources that are not available to us. In addition, some of our competitors may have higher risk tolerances or different risk assessments than we have. These characteristics could allow our competitors to consider a wider variety of investments, establish more relationships and offer better pricing and more flexible structuring than we are able to do. We may lose investment opportunities if we do not match our competitors' pricing, terms and structure. If we are forced to match our competitors' pricing, terms and structure, we may not be able to achieve acceptable returns on our investments or may bear substantial risk of capital loss. A significant part of our competitive advantage stems from the fact that the market for investments in LMM companies is underserved by traditional commercial banks and other financing sources. A significant increase in the number and/or the size of our competitors in this target

Table of Contents

market could force us to accept less attractive investment terms. Furthermore, many of our competitors have greater experience operating under, or are not subject to, the regulatory restrictions that the 1940 Act imposes on us as a BDC.

Table of Contents

We are dependent upon our key investment personnel for our future success.

       We depend on the members of our investment team, particularly Vincent D. Foster, Todd A. Reppert, Rodger A. Stout,Dwayne L. Hyzak, Curtis L. Hartman, Dwayne L. Hyzak and David L. Magdol, Nicholas T. Meserve, Robert M. Shuford and Rodger A. Stout for the identification, review, final selection, structuring, closing and monitoring of our investments. These employees have significant investment expertise and relationships that we rely on to implement our business plan. Although we have entered into a non-compete agreement with Mr. Foster, we have no guarantee that he or any other employees will remain employed with us. If we lose the services of these individuals, we may not be able to operate our business as we expect, and our ability to compete could be harmed, which could cause our operating results to suffer.

Our success depends on attracting and retaining qualified personnel in a competitive environment.

       Our growth will require that we retain new investment and administrative personnel in a competitive market. Our ability to attract and retain personnel with the requisite credentials, experience and skills depends on several factors including, but not limited to, our ability to offer competitive wages, benefits and professional growth opportunities. Many of the entities, including investment funds (such as private equity funds and mezzanine funds) and traditional financial services companies, with which we compete for experienced personnel have greater resources than we have.

       The competitive environment for qualified personnel may require us to take certain measures to ensure that we are able to attract and retain experienced personnel. Such measures may include increasing the attractiveness of our overall compensation packages, altering the structure of our compensation packages through the use of additional forms of compensation, or other steps. The inability to attract and retain experienced personnel would have a material adverse effect on our business.

Our business model depends to a significant extent upon strong referral relationships, and our inability to maintain or develop these relationships, as well as the failure of these relationships to generate investment opportunities, could adversely affect our business.

       We expect that members of our management team will maintain their relationships with intermediaries, financial institutions, investment bankers, commercial bankers, financial advisors, attorneys, accountants, consultants and other individuals within our network, and we will rely to a significant extent upon these relationships to provide us with potential investment opportunities. If our management team fails to maintain its existing relationships or develop new relationships with sources of investment opportunities, we will not be able to grow our investment portfolio. In addition, individuals with whom members of our management team have relationships are not obligated to provide us with investment opportunities, and, therefore, there is no assurance that such relationships will generate investment opportunities for us.

We have a limited operating history as a BDC and as a RIC.There are significant potential conflicts of interest which could impact our investment returns.

       The 1940 Act imposes numerous constraints on the operations of BDCs. Prior to the completionOur executive officers and employees, in their capacities as personnel of the IPO,Investment Manager, may manage other investment funds that operate in the same or a related line of business as we diddo. Accordingly, they may have obligations to such other entities, the fulfillment of which obligations may not operate,be in the best interests of us or our stockholders. In May 2012, we and our management team had no experience operating, asthe Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non-publicly-traded BDC underwhose registration statement on Form N-2 was declared effective by the 1940 Act or as a RIC under Subchapter MSEC in June 2012, to provide certain investment advisory services to HMS Adviser. Under the investment sub-advisory agreement, the Investment Manager is entitled to 50% of the Code. Ourbase management team's limited experience in managing a portfolio of assetsfee and the incentive fees earned by HMS Adviser under such constraints may hinder our ability to take advantage of attractive investment opportunities and, as a result, achieve our investment objective. Furthermore, any failure to complyits advisory agreement with the requirements imposed on BDCs by the 1940 Act could cause the SEC to bring an enforcement action against us. If we do not remain a BDC, we might be regulated as a registered closed-end investment company under the 1940 Act, which would further decrease our operating flexibility.HMS

Table of Contents

Income. However, for the one-year period from the effective date of HMS Adviser's registration statement on Form N-2 through June 4, 2013, the Investment Manager has agreed to waive all such fees to the extent that distributions declared and payable by HMS Income would represent a return of capital for purposes of U.S. federal income tax. As a result, as of December 31, 2012, the Investment Manager has not received any base management fee or incentive fees under the investment sub-advisory agreement and the Investment Manager is not due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement. The sub-advisory relationship requires the Investment Manager to commit resources to achieving HMS Income's investment objective, while such resources were previously solely devoted to achieving our investment objective. Our investment objective and investment strategies are very similar to those of HMS Income and it is likely that an investment appropriate for us or HMS Income would be appropriate for the other entity. As a result, the Investment Manager may face conflicts in allocating investment opportunities between us and HMS Income. Although the Investment Manager will endeavor to allocate investment opportunities in a fair and equitable manner, it is possible that, in the future, we may not be given the opportunity to participate in investments made by other investment funds managed by our officers or employees, such as HMS Income. In any such case, when the Investment Manager identifies an investment, it will be forced to choose which investment fund should make the investment. We have implemented an allocation policy to ensure the equitable distribution of such investment opportunities. We have applied to the SEC for exemptive relief to co-invest with HMS Income, and if the relief is granted, we intend to make such co-investments in accordance with the allocation percentage approved by the independent members of each company's board of directors.

Regulations governing our operation as a BDC will affect our ability to, and the way in which we, raise additional capital.

       Our business will require capital to operate and grow. We may acquire such additional capital from the following sources:

       Senior Securities.    We may issue debt securities or preferred stock and/or borrow money from banks or other financial institutions, which we refer to collectively as senior securities. As a result of issuing senior securities, we will be exposed to additional risks, including the following:

•

Under the provisions of the 1940 Act, we are permitted, as a BDC, to issue senior securities only in amounts such that our asset coverage, as defined in the 1940 Act, equals at least 200% immediately after each issuance of senior securities. If the value of our assets declines, we may be unable to satisfy this test. If that happens, we will be prohibited from issuing debt securities or preferred stock and/or borrowing money from banks or other financial institutions and may not be permitted to declare a dividend or make any distribution to stockholders or repurchase shares until such time as we satisfy this test.



•

Any amounts that we use to service our debt or make payments on preferred stock will not be available for dividends to our common stockholders.



•

It is likely that any senior securities or other indebtedness we issue will be governed by an indenture or other instrument containing covenants restricting our operating flexibility. Additionally, some of these securities or other indebtedness may be rated by rating agencies, and in obtaining a rating for such securities and other indebtedness, we may be required to abide by operating and investment guidelines that further restrict operating and financial flexibility.



•

We and, indirectly, our stockholders will bear the cost of issuing and servicing such securities and other indebtedness.



•

Preferred stock or any convertible or exchangeable securities that we issue in the future may have rights, preferences and privileges more favorable than those of our common stock, including separate voting rights and could delay or prevent a transaction or a change in control to the detriment of the holders of our common stock.

Table of Contents

       Additional Common Stock.    We are not generally able to issue and sell our common stock at a price below net asset value per share. We may, however, sell our common stock, warrants, options or rights to acquire our common stock, at a price below the current net asset value of the common stock if our Board of Directors determines that such sale is in the best interests of our stockholders, and our stockholders approve such sale. See "— Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock" for a discussion of proposals approved by our stockholders that permit us to issue shares of our common stock below net asset value. We may also make rights offerings to our stockholders at prices per share less than the net asset value per share, subject to applicable requirements of the 1940 Act. If we raise additional funds by issuing more common stock or senior securities convertible into, or exchangeable for, our common stock, the percentage ownership of our stockholders at that time would decrease, and they may experience dilution. Moreover, we can offer no assurance that we will be able to issue and sell additional equity securities in the future, on favorable terms or at all.

The Funds are licensed by the SBA, and therefore subject to SBA regulations.

       MSMF our wholly owned subsidiary, and MSC II, our majority-owned subsidiary,wholly owned subsidiaries, are licensed to act as SBICs and are regulated by the SBA. The SBA also places certain limitations on the financing terms of investments by SBICs in portfolio companies and prohibits SBICs from providing funds for certain purposes or to businesses in a few prohibited industries. Compliance with SBA requirements may cause the Funds to forego attractive investment opportunities that are not permitted under SBA regulations.

Table of Contents

       Further, the SBA regulations require that a licensed SBIC be periodically examined and audited by the SBA to determine its compliance with the relevant SBA regulations. The SBA prohibits, without prior SBA approval, a "change of control" of an SBIC or transfers that would result in any person (or a group of persons acting in concert) owning 10% or more of a class of capital stock of a licensed SBIC. If the Funds fail to comply with applicable SBIC regulations, the SBA could, depending on the severity of the violation, limit or prohibit their use of debentures, declare outstanding debentures immediately due and payable, and/or limit them from making new investments. In addition, the SBA can revoke or suspend a license for willful or repeated violation of, or willful or repeated failure to observe, any provision of the Small Business Investment Act of 1958 or any rule or regulation promulgated thereunder. Such actions by the SBA would, in turn, negatively affect us.

Because we borrow money, the potential for gain or loss on amounts invested in us is magnified and may increase the risk of investing in us.

       Borrowings, also known as leverage, magnify the potential for gain or loss on invested equity capital. As we use leverage to partially finance our investments, you will experience increased risks of investing in our common stock.securities. We, through the Funds, issue debt securities guaranteed by the SBA and sold in the capital markets. As a result of its guarantee of the debt securities, the SBA has fixed dollar claims on the assets of the Funds that are superior to the claims of our common stockholders.securities holders. We may also borrow from banks and other lenders, including under our $235 million credit facility (the "Credit Facility").Credit Facility, and may issue debt securities or enter into other types of borrowing arrangements in the future. See "Management's Discussion and Analysis of Financial Condition and Results of Operations — Capital Resources" for a discussion regarding our Credit Facility. If the value of our assets increases, then leveraging would cause the net asset value attributable to our common stock to increase more sharply than it would have had we not leveraged. Conversely, if the value of our assets decreases, leveraging would cause net asset value to decline more sharply than it otherwise would have had we not leveraged our business. Similarly, any increase in our income in excess of interest payable on the borrowed funds would cause our net investment income to increase more than it would without the leverage, while any decrease in our income would cause net investment income to decline more sharply than it would have had we not borrowed. Such a decline could negatively affect our ability to pay common stock dividends.dividends,

Table of Contents

scheduled debt payments or other payments related to our securities. Leverage is generally considered a speculative investment technique.

       As of December 31, 2011,2012, we, through the Funds, had $220$225 million of outstanding indebtedness guaranteed by the SBA, which had a weighted average annualized interest cost of approximately 5.1%4.7% (exclusive of deferred financing costs). The debentures guaranteed by the SBA have a maturity of ten years, with a current weighted average remaining maturity of 6.76.4 years as of December 31, 2011,2012, and require semi-annual payments of interest. We will need to generate sufficient cash flow to make required interest payments on the debentures. If we are unable to meet the financial obligations under the debentures, the SBA, as a creditor, will have a superior claim to the assets of the Funds over our stockholders in the event we liquidate or the SBA exercises its remedies under such debentures as the result of a default by us. In addition, as of December 31, 2011,2012, we had $107$132 million outstanding under our Credit Facility. Borrowings under the Credit Facility bear interest, subject to our election, on a per annum basis equal to (i) the applicable LIBOR rate (0.21% as of December 31, 2012) plus 2.50% or (ii) the applicable base rate (Prime Rate, 3.25% as of December 31, 2012) plus 1.50%. Main Street pays unused commitment fees of 0.375% per annum on the average unused lender commitments under the Credit Facility. If we are unable to meet the financial obligations under the Credit Facility, the Credit Facility lending group will have a superior claim to the assets of MSCC and its subsidiaries (excluding the assets of the Funds) over our stockholders in the event we liquidate or the lending group exercises its remedies under the Credit Facility as the result of a default by us.

Table of Contents

       Illustration.The following table illustrates the effect of leverage on returns from an investment in our common stock assuming various annual returns, net of expenses. The calculations in the table below are hypothetical and actual returns may be higher or lower than those appearing below.

Assumed Return on Our Portfolio(1)
(net of expenses)

(1)

Assumes $737.7 million$1.036 billion in total assets, $327.0$357.0 million in debt outstanding, $411.2$643.0 million in net assets, and an average cost of funds of 4.3%4.0%. Actual interest payments may be different.

(2)

In order for us to cover our annual interest payments on indebtedness, we must achieve annual returns on our December 31, 2012 total assets of at least 1.4%.

       Our ability to achieve our investment objective may depend in part on our ability to access additional leverage on favorable terms by issuing debentures guaranteed by the SBA, through the Funds, or by borrowing from banks or insurance companies, and there can be no assurance that such additional leverage can in fact be achieved.

We may experience fluctuations in our quarterly results.

       We could experience fluctuations in our quarterly operating results due to a number of factors, including our ability or inability to make investments in companies that meet our investment criteria, the interest rate payable on the debt securities we acquire, the level of portfolio dividend and fee income, the level of our expenses, variations in and the timing of the recognition of realized and unrealized gains or losses, the degree to which we encounter competition in our markets and general economic conditions. As a result of these factors, results for any period should not be relied upon as being indicative of performance in future periods.

Table of Contents

Our Board of Directors may change our operating policies and strategies without prior notice or stockholder approval, the effects of which may be adverse.

       Our Board of Directors has the authority to modify or waive our current operating policies, investment criteria and strategies without prior notice and without stockholder approval. We cannot predict the effect any changes to our current operating policies, investment criteria and strategies would have on our business, net asset value, operating results and value of our stock. However, the effects might be adverse, which could negatively impact our ability to pay you dividends and cause you to lose all or part of your investment.

We will be subject to corporate-level income tax if we are unable to qualify as a RIC under Subchapter M of the Code.

       To maintain RIC tax treatment under the Code, we must meet the following annual distribution, income source and asset diversification requirements:

•

The annual distribution requirement for a RIC will be satisfied if we distribute to our stockholders on an annual basis at least 90% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. Depending on the level of taxable income earned in a tax year, we may choose to carry forward taxable income in excess of current year distributions into the next tax year and pay a 4% excise tax on such income. Any such carryover taxable income must be distributed through a dividend declared prior to filing the final tax return related to the year which generated such taxable income. For more information regarding tax treatment, see "Business — Regulation — Taxation as a Regulated Investment Company.Regulation." Because we use debt financing, we are subject to certain asset coverage ratio requirements under the 1940 Act and are (and may in the future become) subject to certain financial covenants under loan and credit agreements that could, under certain circumstances, restrict us from making distributions necessary to satisfy the distribution

requirement. If we are unable to obtain cash from other sources, we could fail to qualify for RIC tax treatment and thus become subject to corporate-level income tax.





•

The source income requirement will be satisfied if we obtain at least 90% of our income for each year from distributions, interest, gains from the sale of stock or securities or similar sources.



•

The asset diversification requirement will be satisfied if we meet certain asset diversification requirements at the end of each quarter of our taxable year. To satisfy this requirement, at least 50% of the value of our assets must consist of cash, cash equivalents, U.S. Government securities, securities of other RICs, and other acceptable securities; and no more than 25% of the value of our assets can be invested in the securities, other than U.S. government securities or securities of other RICs, of one issuer, of two or more issuers that are controlled, as determined under applicable Code rules, by us and that are engaged in the same or similar or related trades or businesses or of certain "qualified publicly traded partnerships."

       Failure to meet these requirements may result in our having to dispose of certain investments quickly in order to prevent the loss of RIC status. Because most of our investments will be in private companies, and therefore will be relatively illiquid, any such dispositions could be made at disadvantageous prices and could result in substantial losses. Moreover, if we fail to maintain RIC tax treatment for any reason and are subject to corporate income tax, the resulting corporate taxes could substantially reduce our net assets, the amount of income available for distribution and the amount of our distributions.

We may not be able to pay you distributions to our stockholders, our distributions may not grow over time, and a portion of distributions paid to youour stockholders may be a return of capital.

       We intend to pay monthly distributions to our stockholders out of assets legally available for distribution. We cannot assure you that we will achieve investment results that will allow us to pay a specified level of cash distributions, previously projected distributions for future periods, or year-to-year increases in cash distributions. Our ability to pay distributions might be adversely affected by, among other things, the impact

Table of Contents

of one or more of the risk factors described herein. In addition, the inability to satisfy the asset coverage test applicable to us as a BDC could limit our ability to pay distributions. All distributions will be paid at the discretion of our Board of Directors and will depend on our earnings, our financial condition, maintenance of our RIC status, compliance with applicable BDC regulations, each of the Funds' compliance with applicable SBIC regulations and such other factors as our Board of Directors may deem relevant from time to time. We cannot assure you that we will pay distributions to our stockholders in the future.

       When we make monthly distributions, we will be required to determine the extent to which such distributions are paid out of current or accumulated earnings, recognized capital gains or capital. To the extent there is a return of capital, investors will be required to reduce their basis in our stock for federal tax purposes, which will result in higher tax liability when the shares are sold, even if they have not increased in value or have lost value. In addition, any return of capital will be net of any sales load and offering expenses associated with sales of shares of our common stock. In the future, our distributions may include a return of capital.

We may have difficulty paying ourthe distributions required distributionsto maintain RIC tax treatment under the Code if we recognize income before or without receiving cash representing such income.

       We will include in income certain amounts that we have not yet received in cash, such as: (i) amortization of original issue discount, which may arise if we receive warrants in connection with the origination of a loan such that ascribing a value to the warrants creates original issue discount in the debt instrument or possibly in other circumstances; (ii) contractual payment-in-kind, or PIK, interest, which represents contractual interest added to the loan balance and due at the end of the loan term; (iii) contractual preferred dividends, which represents contractual dividends added to the preferred stock and due at the end of the preferred stock term; or (iv) amortization of market discount, which is associated with loans purchased in the secondary market at a discount to par value. Such amortization of original issue discounts, increases in loan balances as a result of contractual PIK arrangements, cumulative preferred

Table of Contents

dividends, or amortization of market discount will be included in income before we receive the corresponding cash payments. We also may be required to include in income certain other amounts before we receive such amounts in cash. Investments structured with these features may represent a higher level of credit risk compared to investments generating income which must be paid in cash on a current basis. For the year ended December 31, 2011,2012, (i) approximately 3.7%4.3% of our total investment income was attributable to PIK income not paid currently in cash, (ii) approximately 2.3% of our total investment income was attributable to amortization of original issue discount, (iii) approximately 2.5%0.3% of our total investment income was attributable to contractual preferred dividends,cumulative dividend income not paid currently in cash, and (iv) approximately 0.2%1.4% of our total investment income was attributable to amortization of market discount on loans purchased in the secondary market at a discount.

       Since, in certain cases, we may recognize income before or without receiving cash representing such income, we may have difficulty meeting the annual distribution requirement necessary to maintain RIC tax treatment under the Code. Accordingly, we may have to sell some of our investments at times and/or at prices we would not consider advantageous, raise additional debt or equity capital or forgo new investment opportunities for this purpose. If we are not able to obtain cash from other sources, we may fail to qualify for RIC tax treatment and thus become subject to corporate-level income tax. For additional discussion regarding the tax implications of a RIC, please see "Business — Regulation — Taxation as a Regulated Investment Company.Regulation."

We may in the future choose to pay dividends in our own stock, in which case you may be required to pay tax in excess of the cash you receive.

       We may distribute taxable dividends that are payable in part in our stock. Provided thatUnder certain requirements are satisfied,applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash or in shares of stock (at the stockholders election) would satisfy the Annual Distribution Requirement. The IRS has issued private letter rulings providing that a dividend payable in stock or in cash at the election of the stockholders will be treated as a taxable dividend eligible for the dividends paid deduction provided that at least 20% of the total dividend is payable in cash.cash and certain other requirements are satisfied. Taxable stockholders receiving such

Table of Contents

dividends will be required to include the full amount of the dividend as ordinary income (or as long-term capital gain to the extent such dividend is properly reported as a capital gain dividend) to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives as a distributiondividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

Each of the Funds, as an SBIC, may be unable to make distributions to us that will enable us to meet or maintain RIC status, which could result in the imposition of an entity-level tax.

       In order for us to continue to qualify for RIC tax treatment and to minimize corporate-level taxes, we will be required to distribute substantially all of our net ordinary income and net capital gain income, including income from certain of our subsidiaries, which includes the income from the Funds. We will be partially dependent on the Funds for cash distributions to enable us to meet the RIC distribution requirements. The Funds may be limited by the Small Business Investment Act of 1958, and SBIC regulations governing SBICs, from making certain distributions to us that may be necessary to enable us to maintain our status as a RIC. We may have to request a waiver of the SBA's restrictions for the Funds to make certain distributions to maintain our eligibility for RIC status. We cannot assure you that the SBA will grant such waiver and if the Funds are unable to obtain a waiver, compliance with the SBIC regulations may result in loss of RIC tax treatment and a consequent imposition of an entity-level tax on us.

Table of Contents

Because we intend to distribute substantially all of our income to our stockholders to maintain our status as a RIC, we will continue to need additional capital to finance our growth, and regulations governing our operation as a BDC will affect our ability to, and the way in which we, raise additional capital.capital and make distributions.

       In order to satisfy the requirements applicable to a RIC and to minimize corporate-level taxes, we intend to distribute to our stockholders substantially all of our net ordinary income and net capital gain income. We may carry forward excess undistributed taxable income into the next year, net of the 4% excise tax. Any such carryover taxable income must be distributed through a dividend declared prior to filing the final tax return related to the year which generated such taxable income. As a BDC, we generally are required to meet an asset coverage ratio, as defined in the 1940 Act, of at least 200% immediately after each issuance of senior securities. This requirement limits the amount that we may borrow.borrow and may prohibit us from making distributions. Because we will continue to need capital to grow our investment portfolio, this limitation may prevent us from incurring debt and require us to raise additional equity at a time when it may be disadvantageous to do so.

       While we expect to be able to borrow and to issue additional debt and equity securities, we cannot assure you that debt and equity financing will be available to us on favorable terms, or at all. In addition, as a BDC, we generally are not permitted to issue equity securities priced below net asset value without stockholder approval. If additional funds are not available to us, we could be forced to curtail or cease new investment activities, and our net asset value could decline.

Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock.

       The 1940 Act prohibits us from selling shares of our common stock at a price below the current net asset value per share of such stock, with certain exceptions. One such exception is prior stockholder approval of

Table of Contents

issuances below net asset value provided that our Board of Directors makes certain determinations. AtIn this regard, on June 14, 2012, our 2011 annual meeting ofcommon stockholders our stockholders approved a proposal that authorizesvoted to allow us to sell shares of ourissue common stock at a price below the then current net asset value per share for the period ending on the earlier of (i) June 14, 2013, the one year anniversary of our common stock in one or more offerings for a period2012 annual meeting of one year ending on June 14, 2012.stockholders, and (ii) the date of our 2013 annual meeting of stockholders. Continued access to this exception will require approval of similar proposals at future stockholder meetings. We are seekingdo not currently expect to seek such approval for the next year at our 20122013 annual meeting of stockholders meeting to be held on June 14, 2012.because our common stock price per share has been trading significantly above the current net asset value per share of our common stock. At our 2008 annual meeting of stockholders, our stockholders approved a proposal to authorize us to issue securities to subscribe to, convert to, or purchase shares of our common stock in one or more offerings. Any decision to sell shares of our common stock below the then current net asset value per share of our common stock or securities to subscribe to, convert to, or purchase shares of our common stock would be subject to the determination by our Board of Directors that such issuance is in our and our stockholders' best interests.

       If we were to sell shares of our common stock below net asset value per share, such sales would result in an immediate dilution to the net asset value per share. This dilution would occur as a result of the sale of shares at a price below the then current net asset value per share of our common stock and a proportionately greater decrease in a stockholder's interest in our earnings and assets and voting interest in us than the increase in our assets resulting from such issuance. In addition, if we issue securities to subscribe to, convert to or purchase shares of common stock, the exercise or conversion of such securities would increase the number of outstanding shares of our common stock. Any such exercise would be dilutive on the voting power of existing stockholders, and could be dilutive with regard to dividends and our net asset value, and other economic aspects of the common stock.

       Because the number of shares of common stock that could be so issued and the timing of any issuance is not currently known, the actual dilutive effect cannot be predicted; however, the example below illustrates the effect of dilution to existing stockholders resulting from the sale of common stock at prices below the net asset value of such shares.

Table of Contents

       Illustration: Example of Dilutive Effect of the Issuance of Shares Below Net Asset Value.Assume that Company XYZ has 1,000,000 total shares outstanding, $15,000,000 in total assets and $5,000,000 in total liabilities. The net asset value per share of the common stock of Company XYZ is $10.00. The following table illustrates the reduction to net asset value, or NAV, and the dilution experienced by Stockholder A following the sale of 40,000 shares of the common stock of Company XYZ at $9.50 per share, a price below its NAV per share.

(1)

Assumes that Stockholder A does not purchase additional shares in the sale of shares below NAV.

Changes in laws or regulations governing our operations may adversely affect our business or cause us to alter our business strategy.

       We, the Funds, and our portfolio companies are subject to applicable local, state and federal laws and regulations, including, without limitation, federal immigration laws and regulations. New legislation may be enacted or new interpretations, rulings or regulations could be adopted, including those governing the types of

Table of Contents

investments we are permitted to make, any of which could harm us and our stockholders, potentially with retroactive effect. In addition, any change to the SBA's current debenture SBIC program could have a significant impact on our ability to obtain lower-cost leverage, through the Funds, and therefore, our ability to compete with other finance companies.

       Additionally, any changes to the laws and regulations governing our operations relating to permitted investments may cause us to alter our investment strategy in order to avail ourselves of new or different opportunities. Such changes could result in material differences to the strategies and plans set forth herein and may result in our investment focus shifting from the areas of expertise of our investment team to other types of investments in which our investment team may have less expertise or little or no experience. Thus, any such changes, if they occur, could have a material adverse effect on our results of operations and the value of your investment.

Terrorist attacks, acts of war or natural disasters may affect any market for our common stock,securities, impact the businesses in which we invest and harm our business, operating results and financial condition.

       Terrorist acts, acts of war or natural disasters may disrupt our operations, as well as the operations of the businesses in which we invest. Such acts have created, and continue to create, economic and political uncertainties and have contributed to global economic instability. Future terrorist activities, military or security operations, or natural disasters could further weaken the domestic/global economies and create additional uncertainties, which may negatively impact the businesses in which we invest directly or indirectly and, in turn, could have a material adverse impact on our business, operating results and financial condition. Losses from terrorist attacks and natural disasters are generally uninsurable.

Table of Contents

RISKS RELATED TO OUR INVESTMENTS

Our investments in portfolio companies involve higher levels of risk, and we could lose all or part of our investment.

       Investing in our portfolio companies involves a number of significant risks. Among other things, these companies:

•

may have limited financial resources and may be unable to meet their obligations under their debt instruments that we hold, which may be accompanied by a deterioration in the value of any collateral and a reduction in the likelihood of us realizing any guarantees from subsidiaries or affiliates of our portfolio companies that we may have obtained in connection with our investment, as well as a corresponding decrease in the value of the equity components of our investments;



•

may have shorter operating histories, narrower product lines, smaller market shares and/or significant customer concentrations than larger businesses, which tend to render them more vulnerable to competitors' actions and market conditions, as well as general economic downturns;



•

are more likely to depend on the management talents and efforts of a small group of persons; therefore, the death, disability, resignation, termination, or significant under-performance of one or more of these persons could have a material adverse impact on our portfolio company and, in turn, on us;



•

generally have less predictable operating results, may from time to time be parties to litigation, may be engaged in rapidly changing businesses with products subject to a substantial risk of obsolescence, and may require substantial additional capital to support their operations, finance expansion or maintain their competitive position; and



•

generally have less publicly available information about their businesses, operations and financial condition. We are required to rely on the ability of our management team and investment professionals to obtain adequate information to evaluate the potential returns from investing in these companies. If we are unable to uncover all material information about these companies, we may not make a fully informed investment decision, and may lose all or part of our investment.

Table of Contents

       In addition, in the course of providing significant managerial assistance to certain of our portfolio companies, certain of our officers and directors may serve as directors on the boards of such companies. To the extent that litigation arises out of our investments in these companies, our officers and directors may be named as defendants in such litigation, which could result in an expenditure of funds (through our indemnification of such officers and directors) and the diversion of management time and resources.

The lack of liquidity in our investments may adversely affect our business.

       We invest, and will continue to invest in companies whose securities are not publicly traded, and whose securities will be subject to legal and other restrictions on resale or will otherwise be less liquid than publicly traded securities. The illiquidity of these investments may make it difficult for us to sell these investments when desired. In addition, if we are required to liquidate all or a portion of our portfolio quickly, we may realize significantly less than the value at which we had previously recorded these investments. As a result, we do not expect to achieve liquidity in our investments in the near-term. Our investments are usually subject to contractual or legal restrictions on resale or are otherwise illiquid because there is usually no established trading market for such investments. The illiquidity of most of our investments may make it difficult for us to dispose of them at a favorable price, and, as a result, we may suffer losses.

Table of Contents

We may not have the funds or ability to make additional investments in our portfolio companies.

       We may not have the funds or ability to make additional investments in our portfolio companies. After our initial investment in a portfolio company, we may be called upon from time to time to provide additional funds to such company or have the opportunity to increase our investment through the extension of additional loans, the exercise of a warrant to purchase common stock,equity securities, or the funding of additional equity investments. There is no assurance that we will make, or will have sufficient funds to make, follow-on investments. Any decisions not to make a follow-on investment or any inability on our part to make such an investment may have a negative impact on a portfolio company in need of such an investment, may result in a missed opportunity for us to increase our participation in a successful operation or may reduce the expected yield on the investment.

Our portfolio companies may incur debt that ranks equally with, or senior to, our investments in such companies.

       We invest primarily in the secured term debt as well asof LMM and Middle Market companies and equity issued by LMM and middle market companies. Our portfolio companies may have, or may be permitted to incur, other debt that ranks equally with, or senior to, the debt in which we invest. By their terms, such debt instruments may entitle the holders to receive payment of interest or principal on or before the dates on which we are entitled to receive payments with respect to the debt instruments in which we invest. Also, in the event of insolvency, liquidation, dissolution, reorganization or bankruptcy of a portfolio company, holders of debt instruments ranking senior to our investment in that portfolio company would typically be entitled to receive payment in full before we receive any distribution. After repaying such senior creditors, such portfolio company may not have any remaining assets to use for repaying its obligation to us. In the case of debt ranking equally with debt instruments in which we invest, we would have to share on an equal basis any distributions with other creditors holding such debt in the event of an insolvency, liquidation, dissolution, reorganization or bankruptcy of the relevant portfolio company.

There may be circumstances where our debt investments could be subordinated to claims of other creditors or we could be subject to lender liability claims.

       Even though we may have structured certain of our investments as secured loans, if one of our portfolio companies were to go bankrupt, depending on the facts and circumstances, and based upon principles of equitable subordination as defined by existing case law, a bankruptcy court could subordinate all or a portion of our claim to that of other creditors and transfer any lien securing such subordinated claim to the bankruptcy estate. The principles of equitable subordination defined by case law have generally indicated that

Table of Contents

a claim may be subordinated only if its holder is guilty of misconduct or where the senior loan is re-characterized as an equity investment and the senior lender has actually provided significant managerial assistance to the bankrupt debtor. We may also be subject to lender liability claims for actions taken by us with respect to a borrower's business or instances where we exercise control over the borrower. It is possible that we could become subject to a lender's liability claim, including as a result of actions taken in rendering significant managerial assistance or actions to compel and collect payments from the borrower outside the ordinary course of business.

Second priority liens on collateral securing loans that we make to our portfolio companies may be subject to control by senior creditors with first priority liens. If there is a default, the value of the collateral may not be sufficient to repay in full both the first priority creditors and us.

       Certain loans that we make are secured by a second priority security interest in the same collateral pledged by a portfolio company to secure senior debt owed by the portfolio company to commercial banks or other traditional lenders. Often the senior lender has procured covenants from the portfolio company prohibiting the incurrence of additional secured debt without the senior lender's consent. Prior to and as a condition of permitting the portfolio company to borrow money from us secured by the same collateral pledged to the senior lender, the senior lender will require assurances that it will control the disposition of

Table of Contents

any collateral in the event of bankruptcy or other default. In many such cases, the senior lender will require us to enter into an "intercreditor agreement" prior to permitting the portfolio company to borrow from us. Typically the intercreditor agreements we are requested to execute expressly subordinate our debt instruments to those held by the senior lender and further provide that the senior lender shall control: (1) the commencement of foreclosure or other proceedings to liquidate and collect on the collateral; (2) the nature, timing and conduct of foreclosure or other collection proceedings; (3) the amendment of any collateral document; (4) the release of the security interests in respect of any collateral; and (5) the waiver of defaults under any security agreement. Because of the control we may cede to senior lenders under intercreditor agreements we may enter, we may be unable to realize the proceeds of any collateral securing some of our loans.

       Finally, the value of the collateral securing our debt investment will ultimately depend on market and economic conditions, the availability of buyers and other factors. Therefore, there can be no assurance that the proceeds, if any, from the sale or sales of all of the collateral would be sufficient to satisfy the loan obligations secured by our first or second priority liens. There is also a risk that such collateral securing our investments will decrease in value over time, will be difficult to sell in a timely manner, will be difficult to appraise and will fluctuate in value based upon the success of the portfolio company and market conditions. If such proceeds are not sufficient to repay amounts outstanding under the loan obligations secured by our second priority liens, then we, to the extent not repaid from the proceeds of the sale of the collateral, will only have an unsecured claim against the company's remaining assets, if any.

We are a non-diversified investment company within the meaning of the 1940 Act, and therefore we are not limited with respect to the proportion of our assets that may be invested in securities of a single issuer.

       We are classified as a non-diversified investment company within the meaning of the 1940 Act, which means that we are not limited by the 1940 Act with respect to the proportion of our assets that we may invest in securities of a single issuer. To the extent that we assume large positions in the securities of a small number of issuers, our net asset value may fluctuate to a greater extent than that of a diversified investment company as a result of changes in the financial condition or the market's assessment of the issuer. We may also be more susceptible to any single economic or regulatory occurrence than a diversified investment company. Beyond our RIC asset diversification requirements, we do not have fixed guidelines for diversification, and our investments could be concentrated in relatively few portfolio companies.

Table of Contents

We generally will not control our portfolio companies.

       We do not, and do not expect to, control the decision making in many of our portfolio companies, even though we may have board representation or board observation rights, and our debt agreements may contain certain restrictive covenants. As a result, we are subject to the risk that a portfolio company in which we invest will make business decisions with which we disagree and the management of such company, as representatives of the holders of their common equity, will take risks or otherwise act in ways that do not serve our interests as debt investors. Due to the lack of liquidity for our investments in non-traded companies, we may not be able to dispose of our interests in our portfolio companies as readily as we would like or at an appropriate valuation. As a result, a portfolio company may make decisions that would decrease the value of our portfolio holdings.

Defaults by our portfolio companies will harm our operating results.

       A portfolio company's failure to satisfy financial or operating covenants imposed by us or other lenders could lead to non-payment of interest and other defaults and, potentially, termination of its loans and foreclosure on its secured assets, which could trigger cross-defaults under other agreements and jeopardize a portfolio company's ability to meet its obligations under the debt or equity securities that we hold. We may incur expenses to the extent necessary to seek recovery upon default or to negotiate new terms, which may include the waiver of certain financial covenants, with a defaulting portfolio company.

Table of Contents

Any unrealized depreciation we experience on our loan portfolio may be an indication of future realized losses, which could reduce our income available for distribution.

       As a BDC, we are required to carry our investments at market value or, if no market value is ascertainable, at the fair value as determined in good faith by our Board of Directors. Decreases in the market values or fair values of our investments will be recorded as unrealized depreciation. Any unrealized depreciation in our loan portfolio could be an indication of a portfolio company's inability to meet its repayment obligations to us with respect to the affected loans. This could result in realized losses in the future and ultimately in reductions of our income available for distribution in future periods.

Prepayments of our debt investments by our portfolio companies could adversely impact our results of operations and reduce our return on equity.

       We are subject to the risk that the investments we make in our portfolio companies may be repaid prior to maturity. When this occurs, we will generally reinvest these proceeds in temporary investments, pending their future investment in new portfolio companies. These temporary investments will typically have substantially lower yields than the debt being prepaid and we could experience significant delays in reinvesting these amounts. Any future investment in a new portfolio company may also be at lower yields than the debt that was repaid. As a result, our results of operations could be materially adversely affected if one or more of our portfolio companies elect to prepay amounts owed to us. Additionally, prepayments could negatively impact our return on equity, which could result in a decline in the market price of our common stock.securities.

Changes in interest rates may affect our cost of capital and net investment income.

       Some of our debt investments will bear interest at variable rates and the interest income from these investments could be negatively affected by decreases in market interest rates. In addition, an increase in interest rates would make it more expensive for us to use debt to finance our investments. As a result, a significant increase in market interest rates could increase our cost of capital, which would reduce our net investment income. Also, an increase in interest rates available to investors could make an investment in our common stocksecurities less attractive if we are not able to increase our dividend rate,than alternative investments, a situation which could reduce the value of our common stock.securities. Conversely, a decrease in interest rates may have an adverse impact on our returns by requiring us to seek lower yields on our debt investments and by increasing the risk that our portfolio companies will prepay our debt investments, resulting in the need to redeploy capital at potentially lower rates. A decrease in

Table of Contents

market interest rates may also adversely impact our returns on idle funds, which would reduce our net investment income.

We may not realize gains from our equity investments.

       Certain investments that we have made in the past and may make in the future include warrants or other equity securities. Investments in equity securities involve a number of significant risks, including the risk of further dilution as a result of additional issuances, inability to access additional capital and failure to pay current distributions. Investments in preferred securities involve special risks, such as the risk of deferred distributions, credit risk, illiquidity and limited voting rights. In addition, we may from time to time make non-control, equity investments in portfolio companies. Our goal is ultimately to realize gains upon our disposition of such equity interests. However, the equity interests we receive may not appreciate in value and, in fact, may decline in value. Accordingly, we may not be able to realize gains from our equity interests, and any gains that we do realize on the disposition of any equity interests may not be sufficient to offset any other losses we experience. We also may be unable to realize any value if a portfolio company does not have a liquidity event, such as a sale of the business, recapitalization or public offering, which would allow us to sell the underlying equity interests. We often seek puts or similar rights to give us the right to sell our equity securities back to the portfolio company issuer; however, we may be unable to exercise these puts rights for the consideration provided in our investment documents if the issuer is in financial distress.

Table of Contents

Our marketableMarketable securities and idle funds investments are subject to risks similar to our portfolio company investments.

       Marketable securities and idle funds investments can include, among other things, secured and unsecured debt investments, independently rated debt investments and diversified bond funds. Many of these investments in debt obligations are, or would be if rated, below investment grade quality. Indebtedness of below investment grade quality is regarded as having predominantly speculative characteristics with respect to the issuer's capacity to pay interest and repay principal, similar to our portfolio investments in our portfolio companies. See "— Our investments in portfolio companies involve higher levels of risk, and we could lose all or part of our investment." Many of these marketableMarketable securities and idle funds investments are purchased through over the counter or other markets and are therefore liquid at the time of purchase but may subsequently become illiquid due to events relating to the issuer of the securities, market events, economic conditions or investor perceptions. See "— The lack of liquidity in our investments may adversely affect our business" for a description of risks related to holding illiquid investments. In addition, domestic and foreign markets are complex and interrelated, so that events in one sector of the world markets or economy, or in one geographical region, can reverberate and have materially negative consequences for other market, economic or regional sectors in a manner that may not be foreseen and which may materially affect the market price of our marketableMarketable securities and idle funds investments. Other risks that our portfolio investments are subject to are also applicable to these marketableMarketable securities and idle funds investments.

Our investments in foreign securities may involve significant risks in addition to the risks inherent in U.S. investments.

       Our investments in foreign securities may involve significant risks in addition to the risks inherent in investments in U.S. securities. Our investment strategy contemplates potential investments in debt securities of foreign companies. Investing in foreign companies may expose us to additional risks not typically associated with investing in securities of U.S. companies. These risks include changes in exchange control regulations, political and social instability, expropriation, imposition of foreign taxes, less liquid markets and less available information than is generally the case in the United States, higher transaction costs, less government supervision of exchanges, brokers and issuers, less developed bankruptcy laws, difficulty in enforcing contractual obligations, lack of uniform accounting and auditing standards and greater price volatility.

       Although most of our investments will be U.S. dollar-denominated, any investments denominated in a foreign currency will be subject to the risk that the value of a particular currency will change in relation to

Table of Contents

one or more other currencies. Among the factors that may affect currency values are trade balances, the level of short-term interest rates, differences in relative values of similar assets in different currencies, long-term opportunities for investment and capital appreciation, and political developments.

RISKS RELATING TO OUR COMMON STOCKSECURITIES

Shares of closed-end investment companies, including BDCs, may trade at a discount to their net asset value.

       Shares of closed-end investment companies, including BDCs, may trade at a discount to net asset value. This characteristic of closed-end investment companies and BDCs is separate and distinct from the risk that our net asset value per share may decline. We cannot predict whether our common stock will trade at, above or below net asset value. In addition, if our common stock trades below net asset value, we will generally not be able to issue additional common stock at the market price unless our stockholders approve such a sale and our Board of Directors makes certain determinations. See "— Risks Relating to Our Business and Structure — Stockholders may incur dilution if we sell shares of our common stock in one or more offerings at prices below the then current net asset value per share of our common stock or issue securities to subscribe to, convert to or purchase shares of our common stock" for a discussion of a proposal approved by our stockholders that permits us to issue shares of our common stock below net asset value.

We may be unable to invest a significant portion of the net proceeds from an offering or from exiting an investment or other capital on acceptable terms, which could harm our financial condition and operating results.

       Delays in investing the net proceeds raised in an offering or from exiting an investment or other capital may cause our performance to be worse than that of other fully invested BDCs or other lenders or investors pursuing comparable investment strategies. We cannot assure you that we will be able to identify any investments that meet our investment objective or that any investment that we make will produce a positive return. We may be unable to invest the net proceeds of any offering or from exiting an investment or other capital on acceptable terms within the time period that we anticipate or at all, which could harm our financial condition and operating results.

       We anticipate that, depending on market conditions and the amount of the capital, it may take us a substantial period of time to invest substantially all the capital in securities meeting our investment objective. During this period, we will invest the capital primarily in marketableMarketable securities and idle funds investments, which may produce returns that are significantly lower than the returns which we expect to achieve when our portfolio is fully invested in securities meeting our investment objective. As a result, any distributions that we pay during such period may be substantially lower than the distributions that we may be able to pay when our

Table of Contents

portfolio is fully invested in securities meeting our investment objective. In addition, until such time as the net proceeds of any offering or from exiting an investment or other capital are invested in new securities meeting our investment objective, the market price for our common stocksecurities may decline. Thus, the initial return on your investment may be lower than when, if ever, our portfolio is fully invested in securities meeting our investment objective.

Investing in our common stocksecurities may involve an above average degree of risk.

       The investments we make in accordance with our investment objective may result in a higher amount of risk than alternative investment options and a higher risk of volatility or loss of principal. Our investments in portfolio companies involve higher levels of risk, and therefore, an investment in our sharessecurities may not be suitable for someone with lower risk tolerance.

The market price of our common stocksecurities may be volatile and fluctuate significantly.

       Fluctuations in the trading prices of our sharessecurities may adversely affect the liquidity of the trading market for our sharessecurities and, if we seek to raise capital through future equity financings,securities offerings, our ability to raise such equity

Table of Contents

capital. The market price and liquidity of the market for our common stocksecurities may be significantly affected by numerous factors, some of which are beyond our control and may not be directly related to our operating performance. These factors include:

•

significant volatility in the market price and trading volume of securities of BDCs or other companies in our sector, which are not necessarily related to the operating performance of these companies;



•

changes in regulatory policies, accounting pronouncements or tax guidelines, particularly with respect to RICs, BDCs or SBICs;



•

inability to obtain any exemptive relief that may be required by us in the future from the SEC;



•

loss of our BDC or RIC status or either of the Funds' status as an SBIC;



•

changes in our earnings or variations in our operating results;



•

changes in the value of our portfolio of investments;



•

any shortfall in our investment income or net investment income or any increase in losses from levels expected by investors or securities analysts;



•

loss of a major funding source;



•

fluctuations in interest rates;



•

the operating performance of companies comparable to us;



•

departure of our key personnel;



•

global or national credit market changes; and



•

general economic trends and other external factors.

Provisions of the Maryland General Corporation Law and our articles of incorporation and bylaws could deter takeover attempts and have an adverse impact on the price of our common stock.

       The Maryland General Corporation Law and our articles of incorporation and bylaws contain provisions that may have the effect of discouraging, delaying or making difficult a change in control of our company or the removal of our incumbent directors. The existence of these provisions, among others, may have a negative impact on the price of our common stock and may discourage third-party bids for ownership of our company. These provisions may prevent any premiums being offered to you for our common stock.

Table of Contents

Item 1B.    Unresolved Staff Comments

       None.

Item 2.    Properties

       We do not own any real estate or other physical properties materially important to our operations. Currently, we lease office space in Houston, Texas for our corporate headquarters.

Item 3.    Legal Proceedings

       We may, from time to time, be involved in litigation arising out of our operations in the normal course of business or otherwise. Furthermore, third parties may try to seek to impose liability on us in connection with the activities of our portfolio companies. While the outcome of any current legal proceedings cannot at this time be predicted with certainty, we do not expect any current matters will materially affect our financial condition or results of operations; however, there can be no assurance whether any pending legal proceedings will have a material adverse effect on our financial condition or results of operations in any future reporting period.

Item 4.    Mine Safety Disclosures

       Not applicable.

Table of Contents

PART II

Item 5.    Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities

PRICE RANGE OF COMMON STOCK, HOLDERS AND DISTRIBUTIONS

       Our common stock is traded on the New York Stock Exchange ("NYSE") under the symbol "MAIN." Prior to October 14, 2010, our common stock was traded on the NASDAQ Global Select Market under the same symbol "MAIN." Our common stock began trading on the NASDAQ Global Select Market on October 5, 2007. Prior to that date, there was no established public trading market for our common stock.

       The following table sets forth, for each fiscal quarter during 20112012 and 2010,2011, the range of high and low closing prices of our common stock as reported on the NYSE and on the NASDAQ Global Select Market.NYSE.

       On March 7, 2012,2013 the last sale price of our common stock on the NYSE was $24.27$33.03 per share, and there were approximately 194202 holders of record of the common stock which did not include shareholders for whom shares are held in "nominee" or "street name."

       Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from net asset value per share or at premiums that are unsustainable over the long term are separate and distinct from the risk that our net asset value per share will decrease. It is not possible to predict whether theour common stock will trade at, above, or below net asset value per share. Since our IPO in October 2007, our shares of common stock have traded at prices both less than and exceeding our net asset value per share.

       From our IPO through the third quarter of 2008, we paid quarterly dividends, but in the fourth quarter of 2008 we began paying, and we intend to continue paying,We currently pay monthly dividends to our stockholders. Our monthly dividends, if any, will be determined by our Board of Directors on a quarterly basis.

Table of Contents

       The following table summarizes our dividends declared to date:

Table of Contents

       To obtain and maintain RIC tax treatment, we must, among other things, distribute at least 90% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. We will be subject to a 4% nondeductible federal excise tax on certain undistributed taxable income unless we distribute in a timely manner an amount at least equal to the sum of (1) 98% of our net ordinary income for each calendar year, (2) 98.2% of our capital gain net income for the one-year period ending December 31 in that calendar year and (3) any income recognized, but not distributed, in preceding years (the "Excise Tax Avoidance Requirement"). Dividends declared and paid by us in a year will generally differ from taxable income for that year, as such dividends may include the distribution of current year taxable income, less amounts carried over into the following year, and the distribution of prior year taxable income carried over into and distributed in the current year. For amounts we carry over into the following year, we will be required to pay a 4% excise tax for the excess over 98% of our annual taxable income in excess of distributions for the year. We may retain for investment some or all of our net capital gains (i.e., realized net long-term capital gains in excess of realized net short-term capital losses) and treat such amounts as deemed distributions to our stockholders. If we do this, our stockholders will be treated as if they

Table of Contents

had received actual distributions of the capital gains we retained and then reinvested the net after-tax proceeds in our common stock. In general, our stockholders also would be eligible to claim a tax credit (or, in certain circumstances, a tax refund) equal to their allocable shares of the tax we paid on the capital gains deemed distributed to them. We can offer no assurance that we will achieve results that will permit the payment of any cash distributions and, if we issue senior securities, we may be prohibited from making distributions if doing so causes us to fail to maintain the asset coverage ratios stipulated by the 1940 Act or if distributions are limited by the terms of any of our borrowings.

       Pursuant to a revenue procedure issued by the Internal Revenue Service, or the IRS, the IRS has indicated that it will treat distributions from certain publicly traded RICs (including BDCs)We may distribute taxable dividends that are paidpayable in part in our stock. Under certain applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash and partor in shares of stock as dividends that(at the stockholders election) would satisfy the RIC's annual distribution requirements. In order to qualify for such treatment, the revenue procedure requires that at least 10% of the total distribution be paid in cash and that each stockholder have a right to elect to receive its entire distribution in cash. If too many stockholders elect to receive cash, each stockholder electing to receive cash must receive a proportionate share of the cash to be distributed (although no stockholder electing to receive cash may receive less than 10% of such stockholder's distribution in cash). This revenue procedure applies to distributions declared on or before December 31, 2012, with respect to taxable years ended on or before December 31, 2011.

Table of Contents

       Where theAnnual Distribution Requirement. The IRS revenue procedure is not currently applicable, the IRS has also issued private letter rulings onproviding that a dividend payable in stock or in cash at the election of the stockholders will be treated as a taxable dividend eligible for the dividends paid deduction provided that at least 20% of the total dividend is payable in cash and stockcertain other requirements are satisfied. Taxable stockholders receiving such dividends paid by RICs and real estate investment trusts using a 20% cash standard (and, more recently,will be required to include the 10% cash standardfull amount of the above-referenced IRS revenue procedure)dividend as ordinary income (or as long-term capital gain to the extent such dividend is properly reported as a capital gain dividend), to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives as a dividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if certain requirements are satisfied.a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

       We have adopted a dividend reinvestment plan ("DRIP") that provides for the reinvestment of dividends on behalf of our stockholders, unless a stockholder has elected to receive dividends in cash. As a result, if we declare a cash dividend, our stockholders who have not "opted out" of the DRIP by the dividend record date will have their cash dividend automatically reinvested into additional shares of MSCC common stock. We have the option to satisfy the share requirements of the DRIP through the issuance of new shares of common stock or through open market purchases of common stock by the DRIP plan administrator. Newly-issued shares will be valued based upon the final closing price of MSCC's common stock on a valuation date determined for each dividend by our Board of Directors. Shares purchased in the open market to satisfy the DRIP requirements will be valued based upon the average price of the applicable shares purchased by the DRIP plan administrator, before any associated brokerage or other costs.

SALES OF UNREGISTERED SECURITIES

       During 2011,2012, we issued a total of 348,695229,634 unregistered shares of our common stock in connection with the Final MSC II Exchange pursuant to the exemption from registration provided by Section 4(2) under the Securities Act of 1933. The aggregate value of such shares was approximately $5.3 million.

       During 2012, we issued a total of 349,960 shares of our common stock under the DRIP pursuant to an exemption from the registration requirements of the Securities Act of 1933. The aggregate offering price for the shares of our common stock issued under the DRIP during 20112012 was approximately $6.6$8.9 million.

PURCHASES OF EQUITY SECURITIES

       None.

Table of Contents

STOCK PERFORMANCE GRAPH

       The following graph compares the stockholder return on our common stock from October 5, 2007 to December 31, 20112012 with the Russell 2000 Index and the Main Street Peer Group index.index (as defined below). This comparison assumes $100.00 was invested on October 5, 2007 (the date our common stock began to trade in connection with our initial public offering) in our common stock and in the comparison groups and assumes the reinvestment of all cash dividends prior to any tax effect. The comparisons in the graph below are based on historical data and are not intended to forecast the possible future performance of our common stock.

COMPARISON OF STOCKHOLDER RETURN(1)
Among Main Street Capital Corporation, the Russell 2000 Index and Main Street Peer Group
(For the Period October 5, 2007 to December 31, 2011)2012)

(1)

Total return includes reinvestment of dividends through December 31, 2011.2012.

(2)

The Main Street Peer Group index is composed of American Capital, Strategies, Ltd., Apollo Investment Corporation, Ares Capital Corporation, BlackRock Kelso Capital Corporation, Fidus Investment Corporation, Fifth Street Finance Corp., Gladstone Investment Corporation, Golub Capital BDC, Inc., Gladstone Capital Corporation, Gladstone InvestmentHorizon Technology Finance Corporation, Hercules Technology Growth Capital, Inc., KCAP Financial, Inc., Keating Capital, Inc., Medley Capital Corporation, MCG Capital Corporation, Monroe Capital Corporation, MVC Capital, Inc., NGP Capital Resources Company, New Mountain Finance Corporation, OFS Capital Corporation, PennantPark Floating Rate Capital Ltd., PennantPark Investment Corporation, Prospect Capital Corporation, Saratoga Investment Corp., Solar Capital Ltd., Medallion Financial Corp.Solar Senior Capital Ltd., Stellus Capital Investment Corporation, Triangle Capital Corporation, TCP Capital Corp., THL Credit, Inc., and TICC Capital Corp., Harris & Harris Group, Inc., and WhiteHorse Finance, Inc.

Table of Contents

Item 6.    Selected Financial Data

       The selected financial and other data below reflects the consolidated operations of Main Street and its subsidiaries for the years ended December 31, 2007, 2008,2012, 2011, 2010, 2009 2010, and 2011.2008. The selected financial data at December 31, 2007,2012, 2011, 2010, 2009 and 2008 2009, 2010, and 2011 and for the years ended December 31, 2007,2012, 2011, 2010, 2009 and 2008, 2009, 2010, and 2011, have been derived from consolidated financial statements that have been audited by Grant Thornton LLP, an independent registered public accounting firm. You should read this selected financial and other data in conjunction with our "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the financial statements and related notes included in this Annual Report on Form 10-K.

Table of Contents

Table of Contents

Item 7.    Management's Discussion and Analysis of Financial Condition and Results of Operations

       The following discussion should be read in conjunction with our financial statements and the notes thereto included elsewhere in this Annual Report on Form 10-K.

       Statements we make in the following discussion which express a belief, expectation or intention, as well as those that are not historical fact, are forward-looking statements that are subject to risks, uncertainties and assumptions. Our actual results, performance or achievements, or industry results, could differ materially from those we express in the following discussion as a result of a variety of factors, including the risks and uncertainties we have referred to under the headings "Cautionary Statement Concerning Forward Looking Statements" and "Risk Factors" in Part I of this report.

ORGANIZATION

       Main Street Capital Corporation ("MSCC") was formed on March 9, 2007 for the purpose of (i) acquiring 100% of the equity interests of Main Street Mezzanine Fund, LP ("MSMF") and its general partner, Main Street Mezzanine Management, LLC ("MSMF GP"), (ii) acquiring 100% of the equity interests of Main Street Capital Partners, LLC (the "Investment Manager"), (iii) raising capital in an initial public offering, which was completed in October 2007 (the "IPO"), and (iv) thereafter operating as an internally managed business development company ("BDC") under the Investment Company Act of 1940, as amended (the "1940 Act"). MSMF is licensed as a Small Business Investment Company ("SBIC") by the United States Small Business Administration ("SBA") and the Investment Manager acts as MSMF's manager and investment adviser. Because the Investment Manager, which employs all of the executive officers and other employees of MSCC, is wholly owned by us, we do not pay any external investment advisory fees, but instead we incur the operating costs associated with employing investment and portfolio management professionals through the Investment Manager. The IPO and related transactions discussed above were consummated in October 2007 and are collectively termed the "Formation Transactions."

       On January 7, 2010, MSCC consummated transactions (the "Exchange Offer") to exchange 1,239,695 shares of its common stock for approximately 88% of the total dollar value of the limited partner interests in Main Street Capital II, LP ("MSC II" and, together with MSMF, the "Funds"). Pursuant to the terms of the Exchange Offer, 100% of the membership interests in the general partner of MSC II, Main Street Capital II GP, LLC ("MSC II GP"), were also transferred to MSCC for no consideration. MSC II commenced operations in January 2006, is an investment fund that operates as an SBIC and is also managed by the Investment Manager. During the first quarter of 2012, MSCC exchanged 229,634 shares of its common stock to acquire all of the remaining minority ownership in the total dollar value of the MSC II limited partnership interests, including approximately 5% owned by affiliates of MSCC (the "Final MSC II Exchange"). After the completion of the Final MSC II Exchange, MSCC owns 100% of MSC II. The Exchange Offer and related transactions, including the transfer of the MSC II GP interests and the Final MSC II Exchange, are collectively termed the "Exchange Offer Transactions" (see Note J to the consolidated financial statements). As of December 31, 2011, an approximately 12% minority ownership in the total dollar value of the MSC II limited partnership interests remained outstanding, including approximately 5% owned by affiliates of MSCC. On February 14, 2012, MSCC obtained exemptive relief from the SEC to permit it to acquire the approximately 5% ownership in the total dollar value of the MSC II limited partnership interests held by affiliates of MSCC using the same valuation formula utilized in the Exchange Offer. On February 17, 2012, MSCC acquired a total of approximately 8.5% ownership in the total dollar value of the MSC II limited partnership interests not owned by MSCC, including the approximately 5% held by affiliates of MSCC, in exchange for 170,203 shares of its common stock. After the acquisition of these additional MSC II limited partnership interests on February 17, 2012, an approximately 3.0% minority ownership in the total dollar value of the MSC II limited partnership interests remained outstanding.Transactions."

       MSCC has elected to be treated for federal income tax purposes as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). As a result, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that it distributes to its stockholders as dividends.

       MSCC has direct orand indirect wholly owned subsidiaries that have elected to be taxable entities (the "Taxable Subsidiaries"). The primary purpose of these entities is to hold certain investments that generate "pass

Table of Contents

through" income for tax purposes. The Taxable Subsidiaries are each taxed at their normal corporate tax rates based on their taxable income.

       Unless otherwise noted or the context otherwise indicates, the terms "we," "us," "our" and "Main Street" refer to MSCC and its consolidated subsidiaries, includingwhich include the Funds and the Taxable Subsidiaries.

Table of Contents

OVERVIEW

       We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies which we generally define asand debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies with annual revenues between $10 million and $100 million that operate in diverse industries.industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt instruments,investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States. Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million. Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM and Middle Market portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

       We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the lower middle marketLMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing solutions,options, or a "one stop" financing.financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

       As of December 31, 2012, we had debt and equity investments in 59 LMM portfolio companies with an aggregate fair value of approximately $510.3 million, a total cost basis of approximately $408.0 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.2%. As of December 31, 2012, approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 94% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 90% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 32%. As of December 31, 2011, we had debt and equity investments in 54 LMM portfolio companies with an aggregate fair value of $429.1approximately $415.7 million, with a total cost basis of approximately $362.4$349.0 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.8%. Approximately 75%As of December 31, 2011, approximately 74% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies as of December 31, 2011.companies. At December 31, 2011, we had equity ownership in approximately 94% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 34%. As of December 31, 2010, we had debt and equity investments in 44 LMM portfolio companies with an aggregate fair value of $279.6 million with a total cost basis of approximately $253.0 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.5%. The weighted average annual yields were computed using the effective interest rates for all debt investments atas of December 31, 20112012 and 2010,2011, including amortization of deferred debt origination fees and accretion of

Table of Contents

original issue discount but excluding liquidation fees payable upon repayment of the debt investments and any debt investments on non-accrual status.

       In addition to our LMM investment strategy, we opportunistically pursue investments in privately placed debt securities.Middle Market companies. Our private placementMiddle Market portfolio investments primarily consist of direct or secondary purchases ofinvestments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our privately placedMiddle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have an expected durationa term of between three and fourfive years.

       As of December 31, 2011,2012, we had privately placedMiddle Market portfolio investments in 2785 companies collectively totaling approximately $132.9$390.0 million in fair value with a total cost basis of approximately $133.4$385.5 million. The weighted average revenuesannual revenue for the 27 privately placed85 Middle Market portfolio company investments werewas approximately $367$513.5 million as of December 31, 2011. Our privately placed2012. As of December 31, 2012, almost all of our Middle Market portfolio investments are primarilywere in the form of debt investments and 69%approximately 92% of such debt investments at cost were secured by first priority liens on portfolio

Table of Contents

company assets. The weighted average annual effective yield on our privately placedMiddle Market portfolio debt investments was approximately 10.6%8.8% as of December 31, 2011.2012. As of December 31, 2010,2011, we had privately placedMiddle Market portfolio investments in 1657 companies collectively totaling approximately $67.1$226.5 million in fair value with a total cost basis of approximately $65.6$228.9 million. The weighted average revenuesannual revenue for the 16 privately placed57 Middle Market portfolio company investments was approximately $472.6 million as of December 31, 2011. As of December 31, 2011, almost all of our Middle Market portfolio investments were in the form of debt investments and approximately $352 million.82% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our privately placedMiddle Market portfolio debt investments was approximately 12.5%9.5% as of December 31, 2010.2011. The weighted average yield wasannual yields were computed using the effective interest rates for all debt investments atas of December 31, 20112012 and 2010,2011, including amortization of deferred debt origination fees and accretion of original issue discount but excluding liquidation fees payable upon repayment.repayment of the debt investments.

       As of December 31, 2012, we had Other Portfolio investments in 3 companies collectively totaling approximately $24.1 million in fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our investment portfolio at fair value as of December 31, 2012. As of December 31, 2011, we had Other Portfolio investments in 3 companies collectively totaling approximately $14.1 million in both fair value and cost basis and which comprised 2.1% of our investment portfolio at fair value as of December 31, 2011.

       Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes. An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF is a wholly owned subsidiary of MSCC and MSC II is a majorityare both wholly owned subsidiarysubsidiaries of MSCC.

       The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

       During 2011, we paid dividends onMSCC and its consolidated subsidiaries are internally managed by the Investment Manager, a monthly basis totaling $1.56 per share, or $34.9 million. We generated undistributed taxable income (or "spillover income")wholly owned subsidiary of approximately $7.9 million, or $0.30 per share, during 2011 that will be carried forward toward distributions paid in 2012. In December 2011, we declared monthly dividends for the first quarter of 2012 totaling $0.405 per share, representing an 8% increase compared to the monthly dividends for the first quarter of 2011. In March 2012, we declared monthly dividends for the second quarter of 2012 totaling $0.42 per share, representing a 7.7% increase compared to the monthly dividends for the second quarter of 2011. During 2010, we paid monthly dividends of $0.125 per share, or $1.50 per share for the entire year. Including the dividends declared for the first and second quarters of 2012, we will have paid approximately $7.14 per share in cumulative dividends since our October 2007 initial public offering.

       At December 31, 2011, we had $42.7 million in cash and cash equivalents and $120.5 million in marketable securities and idle funds investments. In the fourth quarter of 2011, we expanded our credit facility (the "Credit Facility"), from $155 million to $235 million to provide additional liquidity in support of future investment and operational activities. The $80 million increase in total commitments included commitment increases by lenders currently participating in the Credit Facility, as well as the addition of two new lender relationshipsMSCC, which further diversified our lending group to a total of eight participants.

       In October 2011, we completed a follow-on public stock offering in which we sold 3,450,000 shares of common stock, including the underwriters' full exerciseemploys all of the over-allotment option, at a price toexecutive officers and other employees of Main Street. Because the public of $17.50 per share (or approximately 123% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $57.5 million, after deducting underwriters' commissions and offering costs. In March 2011, we completed a follow-on public stock offering in which we sold 4,025,000 shares of common stock, including the underwriters' full exercise of the over-allotment option, at a price to the public of $18.35 per share (or approximately 141% of the then latest reported Net Asset Value per share), resultingInvestment Manager is wholly owned by MSCC, Main Street does not pay any external

Table of Contents

in total net proceeds of approximately $70.3 million, after deducting underwriters' commissionsinvestment advisory fees, but instead incurs the operating costs associated with employing investment and offering costs.

       A proposed bill in the U.S. House of Representatives, the Small Business Investment Company Modernization Act of 2011, or House Bill 3219, would increase the total SBIC leverage capacity for affiliated SBIC funds from $225 million to $350 million. Another bill in the U.S. Senate, Senate Bill 2136, to increase the total SBIC leverage capacity for affiliated SBIC funds to $350 million was recently introduced in the U.S. Senate and referred to the Committee on Small Business and Entrepreneurship. If either of these bills is enacted, Main Street's SBIC leverage capacityportfolio management professionals through the Funds would increaseInvestment Manager. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio. For the years ended December 31, 2012 and 2011, the ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.8% and 2.2% respectively.

       In addition, during May 2012, we and the Investment Manager executed an investment sub-advisory agreement with HMS Adviser, LP, which is the investment advisor to HMS Income Fund, Inc., a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by an additional $125 million. While Main Street is positionedthe SEC in June 2012, to benefitprovide certain investment advisory services to HMS Adviser, LP. We are initially providing such investment advisory services to HMS Adviser, LP, but ultimately intend that the Investment Manager provide such services because the fees we receive from such arrangement could otherwise have negative consequences on our ability to meet the source-of-income requirement necessary for us to maintain our RIC tax treatment. We will need to obtain certain relief from the full passage of either bill,SEC before the ultimate form and likely outcome ofInvestment Manager is permitted to provide these services to HMS Adviser, LP, which we are seeking, but there can be no assurance that we will obtain such legislation or any similar legislation cannot be predicted.relief.

CRITICAL ACCOUNTING POLICIES

Basis of Presentation

       Our financial statements are prepared in accordance with U.S. generally accepted accounting principles in the United States of America ("U.S. GAAP"). For the three years ended December 31, 2012, 2011 and 2010, our consolidated financial statements include the accounts of MSCC and its consolidated subsidiaries, includingwhich include the Funds.Funds and the Taxable Subsidiaries. Portfolio investments, as used herein, refers to all of our portfolio investments in LMM companies, private placementMiddle Market portfolio investments, Other Portfolio investments and our investment in the Investment Manager but excludes all of our "marketable"Marketable securities and idle funds investments." "MarketableMarketable securities and idle funds investments"investments are classified as financial instruments and are reported separately on our Consolidated Balance Sheets and Consolidated Schedule of Investments due to the nature of such investments. Our results of operations for the three years ended December 31, 2012, 2011 and 2010, cash flows for the three years ended December 31, 2012, 2011 2010, and 2009,2010 and financial position as of December 31, 20112012 and 2010,2011, are presented on a consolidated basis. The effects of all intercompany transactions between Main Street and its consolidated subsidiaries have been eliminated in consolidation. Certain reclassifications have been made to prior period balances to conform with the current financial statement presentation.presentation, including certain investments previously classified as Marketable securities and idle funds investments that are now considered a part of the Middle Market portfolio and are now classified as "Non-Control/Non-Affiliate investments."

       Under the investment company rules and regulations pursuant to Article 6 of Regulation S-X and the Audit and Accounting Guide for Investment Companies issued by the American Institute of Certified Public Accountants (the "AICPA Guide"), we are precluded from consolidating portfolio company investments, including those in which we have a controlling interest, unless the portfolio company is another investment company. An exception to this general principle in the AICPA Guide occurs if we own a controlled operating company that provides all or substantially all of its services directly to us, or to an investment company of ours. None of the investments made by us qualify for this exception. Therefore, our portfolio investments are carried on the balance sheet at fair value, as discussed further in Note B to our consolidated financial statements, with any adjustments to fair value recognized as "Net Change in Unrealized Appreciation (Depreciation)" on our Statement of Operations until the investment is exited,realized, usually upon exit, resulting in any gain or loss on exit being recognized as a "Net Realized Gain (Loss) from Investments."

Table of Contents

Portfolio Investment Valuation

       The most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our portfolio investments and the related amounts of unrealized appreciation and depreciation. As of December 31, 2012 and 2011, and 2010, approximately 76% and 78%, respectively,89% of our total assets at each date represented investments in portfolio companies valued at fair value (including our investment in the Investment Manager). We are required to report our investments at fair value. We follow the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("Codification" or "ASC") 820,Fair Value Measurements and Disclosures ("ASC 820"). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and enhances disclosure requirements for fair value measurements.

       Our portfoliobusiness strategy calls for us to invest primarily in illiquid securities issued by private, LMM companies as well as privately placedand debt securities issued by middle marketMiddle Market companies that are

Table of Contents

generally larger in size than the LMM companies. TheseOur portfolio also includes Other Portfolio investments which primarily consist of investments which are not consistent with the typical profiles for our LMM and Middle Market portfolio investments, including investments which may be managed by third parties. All of our portfolio investments may be subject to restrictions on resale. LMM companiesinvestments and Other Portfolio investments generally have no established trading market while privately placed debtMiddle Market securities generally have established markets that are not active. We determine in good faith the fair value of our portfolio investments pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. For LMM investments, we review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For private placementMiddle Market portfolio debt and Other Portfolio debt investments, we generallyprimarily use observable inputs such as quoted prices in the valuation process. For Other Portfolio equity investments we generally value such investments based on the fair value of the portfolio company as determined by independent third parties, and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of theour portfolio.

       For valuation purposes, control"control" LMM portfolio investments are composed of debt and equity and debt securities in companies for which we have a controlling interest in the portfolio company or have the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we determine the fair value of control investments using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the investments.various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate.generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

Table of Contents

       For valuation purposes, non-control"non-control" LMM portfolio investments are composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations for non-control LMM investments are generally not readily available.available for non-control LMM portfolio investments. For our non-control LMM investments, we use a combination of the market and income approaches to value our equity investments and the income approach to value our debt instruments. For non-controlinvestments similar to the approaches used for our control LMM debtportfolio investments, we determine the fair value primarilyand which includes using a yieldyield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of ana LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yieldyield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yieldyield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the face amount of the LMM debt security. A change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yieldyield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if ana LMM debt security is in workout status, we may consider other factors in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

       Our private placementMiddle Market portfolio investments primarily consist of direct or secondary purchases ofinvestments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our investment portfolio. For valuation purposes, all of our private placementMiddle Market portfolio investments are non-controlnon control investments and are composed of debt securities for which we do not have a controlling interest

Table of Contents

in the portfolio company, or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or other independent pricing. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach that is similar to the income approach using a yield to maturity model used to value our LMM portfolio debt investments.

       For valuation purposes, all of our Other Portfolio investments are non-control investments for which we generally do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. We value our Other Portfolio equity investments based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value of these investments through obtaining third party quotes or other independent pricing. To the extent observable inputs are not available for our Other Portfolio debt investments, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our non-control LMM portfolio debt investments.

       Due to the inherent uncertainty in the valuation process, our determination of fair value for our LMMportfolio investments may differ materially from the values that would have been used had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

Table of Contents

Revenue Recognition

Interest and Dividend Income

       We record interest and dividend income on the accrual basis to the extent amounts are expected to be collected. Dividend income is recorded as dividends are declared or at the point an obligation exists for the portfolio company to make a distribution. In accordance with our valuation policy, we evaluate accrued interest and dividend income periodically for collectability. When a loan or debt security becomes 90 days or more past due, and if we otherwise do not expect the debtor to be able to service all of its debt or other obligations, we will generally place the loan or debt security on non-accrual status and cease recognizing interest income on that loan or debt security until the borrower has demonstrated the ability and intent to pay contractual amounts due. If a loan or debt security's status significantly improves regarding the debtor's ability to service the debt or other obligations, or if a loan or debt security is fully impaired, sold or written off, we will remove it from non-accrual status.

Fee Income

       We may periodically provide services, including structuring and advisory services, to our portfolio companies. For services that are separately identifiable and evidence exists to substantiate fair value, income is recognized as earned, which is generally when the investment or other applicable transaction closes. Fees received in connection with debt financing transactions for services that do not meet these criteria are treated as debt origination fees and are deferred and accreted into interest income over the life of the financing.

Payment-in-Kind ("PIK") Interest and Cumulative Dividends

       We hold debt and preferred equity instruments in our investment portfolio that contain payment-in-kind ("PIK") interest and cumulative dividend provisions. The PIK interest, computed at the contractual rate specified in each debt agreement, is periodically added to the principal balance of the debt and is recorded as interest income. Thus, the actual collection of this interest may be deferred until the time of debt principal repayment. Cumulative dividends are recorded as dividend income, and any unpaid dividends in arrears are added to the balance of the preferred equity investment. The actual collection of these dividends in arrears may be deferred until such time as the preferred equity is redeemed. To maintain RIC tax treatment (as discussed below), these non-cash sources of income may need to be paid out to stockholders in the form of distributions, even though we may not have collected the PIK interest and cumulative dividends in cash. We will stop accruing PIK interest and cumulative dividends and will write off any accrued and uncollected interest and dividends in arrears when it is determined that such PIK interest and dividends in arrears are no longer collectible.

Share-Based Compensation

       We account for our share-based compensation plans using the fair value method, as prescribed by ASC 718,Compensation — Stock Compensation. Accordingly, for restricted stock awards, we measured the grant date fair value based upon the market price of our common stock on the date of the grant and will amortize this fair value to share-based compensation expense over the requisite service period or vesting term.

Table of Contents

Income Taxes

       MSCC has elected to be and intends to continue to qualifytreated for thefederal income tax treatment applicable to,purposes as a RIC. As a RIC, under the Code, and, among other things, intends to make the required distributionsMSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that MSCC distributes to its stockholders as specified therein. In order to qualify as a RIC,dividends. MSCC is required to timelymust generally distribute to its stockholders at least 90% of its investment company taxable income as defined by the Code, each year. Depending on the levelto qualify for pass-through tax treatment and maintain its RIC status. As part of maintaining RIC status, undistributed taxable income earned in a tax year, MSCC may choose(subject to carry forward taxable income in excess of current year distributions into the next tax year and pay a 4% excise tax on such income. Any such carryover taxable income musttax) pertaining to a given fiscal year may be distributed through a dividendup to 12 months subsequent to the end of that fiscal year, provided such dividends are declared prior to the filing of the finalfederal income tax return related tofor the year which generated such taxable income.prior year.

Table of Contents

       The Taxable Subsidiaries hold certain portfolio investments of Main Street.for us. The Taxable Subsidiaries are consolidated with us for U.S. GAAPfinancial reporting purposes, and the portfolio investments held by themthe Taxable Subsidiaries are included in Main Street'sour consolidated financial statements. The principal purpose of the Taxable Subsidiaries is to permit Main Streetus to hold equity investments in portfolio companies which are "pass through" entities for tax purposes in order to comply with the "source income" requirements contained in the RIC tax provisions.provisions of the Code. The Taxable Subsidiaries are not consolidated with Main Streetus for income tax purposes and may generate income tax expense or income tax benefit as a result of their ownership of certainvarious portfolio investments. This income tax expense or benefit, if any, is reflected in Main Street'sour Consolidated Statement of Operations.

       The Taxable Subsidiaries use the liability method in accounting for income taxes. Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements, using statutory tax rates in effect for the year in which the temporary differences are expected to reverse. A valuation allowance is provided against deferred tax assets when it is more likely than not that some portion or all of the deferred tax asset will not be realized.

       Taxable income generally differs from net income for financial reporting purposes due to temporary and permanent differences in the recognition of income and expenses. Taxable income generally excludes net unrealized appreciation or depreciation, as investment gains or losses are not included in taxable income until they are realized.

PORTFOLIO INVESTMENT COMPOSITION

       LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies. The LMM debt investments are primarily secured by either a first or second lien on the assets of the portfolio company, generally bear interest at fixed rates, and generally mature between five and seven years from the original investment date. In most LMM portfolio companies, we also receive nominally priced equity warrants and/or make direct equity investments, usually in connection with a debt investment.

       Private placementMiddle Market portfolio investments primarily consist of direct or secondary purchases ofinvestments in interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our privately placedMiddle Market portfolio debt investments are generally secured by either a first or second priority lien.

       Summaries ofThe following table summarizes the composition of our LMM investment portfolio, private placementMiddle Market investment portfolio, and total combined LMM and Middle Market investment portfolio at cost and fair value by type of investment as a percentage of the total LMM investment portfolio, the total Middle Market investment portfolio and the total combined LMM and Middle Market investment portfolio as of December 31, 2012 and 2011 (this information excludes the Other Portfolio investments and the Investment Manager).