UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One):

For the fiscal year ended December 31, 20122013

For the transition period from              to             

Commission File Number: 001-14195

American Tower Corporation

(Exact name of registrant as specified in its charter)

116 Huntington Avenue

Boston, Massachusetts 02116

(Address of principal executive offices)

Telephone Number (617) 375-7500

(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  x    No  ¨

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  ¨    No  x

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  x    No  ¨

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  x    No  ¨

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 the Form 10-K or any amendment to this Form 10-K.  x

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 definition of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check One):

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act):    Yes  ¨    No  x

The aggregate market value of the voting and non-voting common stock held by non-affiliates of the registrant as of June 30, 20122013 was approximately $27.6$28.7 billion, based on the closing price of the registrant’s common stock as reported on the New York Stock Exchange as of the last business day of the registrant’s most recently completed second quarter.

As of February 11, 2013,14, 2014, there were 395,103,065395,017,519 shares of common stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive proxy statement (the “Definitive Proxy Statement”) to be filed with the Securities and Exchange Commission relative to the Company’s 20132014 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report.

AMERICAN TOWER CORPORATION

TABLE OF CONTENTS

FORM 10-K ANNUAL REPORT

FISCAL YEAR ENDED DECEMBER 31, 20122013

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AMERICAN TOWER CORPORATION

TABLE OF CONTENTS—(Continued)

FORM 10-K ANNUAL REPORT

FISCAL YEAR ENDED DECEMBER 31, 20122013

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report contains statements about future events and expectations, or forward-looking statements, all of which are inherently uncertain. We have based those forward-looking statements on our current expectations and projections about future results. When we use words such as “anticipates,” “intends,” “plans,” “believes,” “estimates,” “expects” or similar expressions, we do so to identify forward-looking statements. Examples of forward-looking statements include statements we make regarding future prospects of growth in the communications site leasing industry, the level of future expenditures by companies in this industry and other trends in this industry, the effects of consolidation among companies in our industry and among our tenants and other competitive pressures, changes in zoning, tax and other laws and regulations, economic, political and other events, particularly those relating to our international operations, our substantial leverage and debt service obligations, our future financing transactions, our plans to fund our future liquidity needs, the level of future expenditures by companies in this industry and other trends in this industry, our ability to maintain or increase our market share, our future operating results, our ability to qualify or to remain qualified for taxation as a real estate investment trust (“REIT”), our substantial leverage and debt service obligations, economic, political and other events, particularly those relating to our international operations, changes in environmental, tax and other laws, our ability to protect our rights to the land under our towers, natural disasters and similar events, the amount and timing of any future distributions including those we are required to make as a REIT, our future capital expenditure levels, our ability to protect our rights to the land under our towers, natural disasters and similar events and our future purchases under our stock repurchase program, our future capital expenditure levels, our future financing transactions and our plans to fund our future liquidity needs.program. These statements are based on our management’s beliefs and assumptions, which in turn are based on currently available information. These assumptions could prove inaccurate. These forward-looking statements may be found under the captions “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as in this Annual Report generally.

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You should keep in mind that any forward-looking statement we make in this Annual Report or elsewhere speaks only as of the date on which we make it. New risks and uncertainties arise from time to time, and it is impossible for us to predict these events or how they may affect us. In any event, these and other important factors, including those set forth in Item 1A of this Annual Report under the caption “Risk Factors,” may cause actual results to differ materially from those indicated by our forward-looking statements. We have no duty to, and do not intend to update or revise the forward-looking statements we make in this Annual Report, except as may be required by law. In light of these risks and uncertainties, you should keep in mind that the future events or circumstances described in any forward-looking statement we make in this Annual Report or elsewhere might not occur. References in this Annual Report to “we,” “our” and “the Company”the “Company” refer to American Tower Corporation and its predecessor, as applicable, individually and collectively with its subsidiaries as the context requires.

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PART I

Overview

We are a leading independent owner, operator and developer of wireless and broadcast communications real estate. Our primary business is leasing antenna space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. We refer to this business as our rental and management operations, which accounted for approximately 97%98% of our total revenues for the year ended December 31, 2012. We also2013. Through our network development services, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites. EffectiveSince January 1, 2012, we reorganized to qualifyhave been organized and have qualified as a REIT for federal income tax purposes (the “REIT Conversion”).purposes.

Our communications real estate portfolio of 54,60467,418 communications sites, as of December 31, 2012,2013, includes wireless and broadcast communications towers and distributed antenna system (“DAS”) networks, which provide seamless coverage solutions in certain in-building and outdoor wireless environments. Our portfolio primarily consists of towers that we own and towers that we operate pursuant to long-term lease arrangements, including, as of December 31, 2012, 22,5342013, 27,739 towers domestically and 31,78939,330 towers internationally. In addition, ourOur portfolio also includes 281349 DAS networks thatnetworks. In addition to the communications sites in our portfolio, we operate primarily in malls and casinos, and select outdoor environments. We also manage rooftop and tower sites for property owners under various contractual arrangements as well asand hold property interests that we lease to communications service providers and third-party tower operators.

American Tower Corporation was originally created as a subsidiary of American Radio Systems Corporation in 1995 and was spun off into a free-standing public company in 1998. Since inception, we have grown our communications real estate portfolio through acquisitions, long-term lease arrangements and site development. In October 2013, we significantly expanded our portfolio through our acquisition of MIP Tower Holdings LLC (“MIPT”), a private REIT and parent company to Global Tower Partners (“GTP”), an owner and operator of approximately 5,370 communications sites, through its various operating subsidiaries, in the United States, Costa Rica and Panama. GTP also manages rooftops and holds property interests that it leases to communications service providers and third-party tower operators. We believe the acquisition provides us with key strategic and financial advantages, due to the high quality of the assets, which are in locations complementary to our portfolio. For more information on our acquisition of MIPT, see note 6 to our consolidated financial statements included in this Annual Report.

We are a holding company and conduct our operations through our directly and indirectly owned subsidiaries and joint ventures. Our principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. We conduct our international operations through our subsidiary, American Tower International, Inc., which in turn conducts operations through its various international holding and operating subsidiaries and joint ventures. Our international operations consist of our operations in Brazil, Chile, Colombia, Costa Rica, Germany, Ghana, India, Mexico, Panama, Peru, South Africa and Uganda.

Our continuing operations are reported in three segments: domestic rental and management, international rental and management and network development services. For more information about our business segments, as well as financial information about the geographic areas in which we operate, see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and note 2021 to our consolidated financial statements included in this Annual Report.

We hold and operate certain of our assets through one or more taxable REIT subsidiaries (“TRSs”). A TRS is a subsidiary of a REIT that is subject to applicable corporate income tax. Our use of TRSs enables us to continue to engage in certain businesses while complying with REIT qualification requirements and also allows us to retain income generated by these businesses for reinvestment without the requirement of distributing those earnings. The non-REIT qualified businesses that we hold through TRSs include most of our network development services segment. In addition, we have included most of our international operations and managed networks business within our TRSs.

We are currently considering changingmay, from time to time, change the election of one or more of our previously designated TRSs which hold certain of our international operations, to be treated as qualified REIT subsidiaries or other disregarded entities (“QRSs”), and may reorganize and transfer certain assets or operations from our TRSs to other subsidiaries, including QRSs.

As a REIT, we generally will not We changed the previous TRS election for certain of our Mexican subsidiaries to be subject to federal income taxes on our income and gains that we distribute to our stockholders, including the income derived from leasing towers. However, eventreated as a REIT, we will remain obligated to pay income taxes on earnings from our TRS assets.QRSs as of March 1, 2013. In addition, we restructured certain of our international assets and operations continuedomestic TRSs to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted.

Annually,treated as a REIT, we are required to distribute to our stockholders an amount equal to at least 90%QRSs as of our REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Our REIT taxable income typically will not include income earned by our TRSs except to the extent the TRSs pay dividends. In 2012, we paid regular cash distributions of an aggregate of approximately $355.6 million to our stockholders. We intend to continue paying regular distributions in 2013. The amount, timing and frequency of future distributions will be at the sole discretion of our Board of Directors and will be declared based upon various factors, a number of which may be beyond our control, including our financial condition and operating cash flows, the amount required to maintain REIT status and reduce any income and excise taxes that we otherwise would be required to pay, limitations on distributions in our existing and future debt instruments, our ability to utilize net operating losses (“NOLs”) to offset, in whole or in part, our distribution requirements, limitations on our ability to fund distributions using cash generated through our TRSs and other factors that our Board of Directors may deem relevant.January 1, 2014.

Products and Services

Rental and Management Operations

Our rental and management operations accounted for approximately 97%98%, 98%97% and 98% of our total revenues for the years ended December 31, 2013, 2012 2011 and 2010,2011, respectively. Our tenants lease space on our communications site infrastructure,real estate, where they install and maintain their individual communications network equipment. Our revenue is primarily generated from tenant leases. The annual rental payments vary considerably depending upon numerous factors, including, but not limited to, tower location, amount and type of tenant equipment on the tower, ground space required by the tenant and remaining tower capacity. Our tenant leases are typically non-cancellable and have annual rent escalations. Our primary costs typically include ground rent (which is primarily fixed, with annual cost escalations), property taxes and repairs and maintenance. In most of our international markets, a portion of our operating costs is passed through to our tenants, such as ground rent or fuel costs. Our rental and management operations have generated consistent incremental growth in revenue and have low cash flow volatility due to the following characteristics:

Our domestic rental and management segment is comprised of our nationwide network of communications sites that enablesenable us to address the needs of national, regional, local and emerging communications service providers in the United States, as well as customers in a number of other industries. Our domestic rental and management segment also includes property interests that we lease to communications service providers and third-party tower operators. Our domestic rental and management segment accounted for approximately 67%65%, 72%67% and 79%72% of our total revenues for the years ended December 31, 2013, 2012 2011 and 2010,2011, respectively.

Our international rental and management segment, which is comprised of communications sites in Brazil, Chile, Colombia, Costa Rica, Germany, Ghana, India, Mexico, Panama, Peru, South Africa and Uganda, provides a source of growth and diversification, and growth.including exposure to markets in various stages of wireless network development. Our international rental and management segment accounted for approximately 30%33%, 26%30% and 19%26% of our total revenues for the years ended December 31, 2013, 2012 2011 and 2010,2011, respectively.

Our rental and management operations include the operation of wireless and broadcast communications towers and managed networks, rooftop management, the leasing of property interests and the installationprovision of backup power through shared generators domestically.

Communications Towers.We own and operate communications towers in the United States, Brazil, Chile, Colombia, Germany, Ghana, India, Mexico, Peru, South Africa and Uganda. Approximately 96%, 98%96% and 98% of revenue in our rental and management segments was attributable to our communications towers for the years ended December 31, 2013, 2012 2011 and 2010,2011, respectively.

We lease real estate on our communications towers to tenants providing a diverse range of communications services, including personal communications services, cellular voice and data, broadcasting, enhanced specialized mobile radio WiMAX, paging and fixed microwave. Our top domestic and international tenants by revenue are as follows:

Accordingly, we are subject to certain risks, as set forth in Item 1A of this Annual Report under the caption “Risk Factors—A substantial portion of our revenue is derived from a small number of tenants, and we are sensitive to changes in the creditworthiness and financial strength of our tenants.” In addition, we are subject to risks related to our international operations, as set forth under the caption “Risk Factors—Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.”

Managed Networks, Rooftop Management, Property Interests and Shared Generators.In addition to our communications sites, we also own and operate several types of managed network solutions, provide

communications site management services to third parties, manage and/or lease property interests under carrier or other third-party communications sites and provide back-up power sources to tenants at our sites.

Network Development Services

Through our network development services segment, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites. This segment accounted for approximately 3%2%, 2%3% and 2% of our total revenues for the years ended December 31, 2013, 2012 2011 and 2010,2011, respectively.

Site Acquisition, Zoning and Permitting. We engage in site acquisition services on our own behalf in connection with our tower development projects, as well as on behalf of our tenants. We typically work with our tenants’ engineers to determine the geographic areas where new tower sites will best address the tenants’ needs and meet their coverage objectives. Once a new site is identified, we acquire the rights to the land or structure on which the site will be constructed, and we manage the permitting process to ensure all necessary approvals are obtained to construct and operate the communications site.

Structural Analysis.We offer structural analysis services to wireless carriers in connection with the installation of their communications equipment on our towers. Our team of engineers can evaluate whether a tower structure can support the additional burden of the new equipment or if an upgrade is needed, which enables our tenants to better assess potential sites before making an installation decision. Our structural analysis capabilities enable us to provide higher quality service to our existing tenants by, among other things, reducing the time required to achieve operational readiness, while also providing opportunities to offer structural analysis services to third parties.

Strategy

Operational Strategy

Our operational strategy is to capitalize on the global growth in the use of wireless communications services and the evolution of advanced wireless handsets, tablets and other mobile devices, as well asand the expanding

corresponding expansion of communications infrastructure required to deploy current and future generations of wireless communications technologies. To

achieve this, our primary focus is to (i) increase the leasing of our existing communications real estate portfolio, (ii) invest in and selectively grow our communications real estate portfolio, (iii) further improve upon our operational performance and (iv) maintain a strong balance sheet. We believe these efforts will further support and enhance our ability to capitalize on the growth in demand for wireless infrastructure.

resulted in significant capital spending by major wireless carriers. As a result, we anticipate consistent demand for our communications sites because they are attractively located for wireless service providers and have capacity available for additional tenants. In the United States, incremental carrier capital spending is being driven primarily by the build-out of fourth generation (4G) networks, while our international markets are in various stages of network development. As of December 31, 2013, we had a global average of approximately 1.9 tenants per tower. We believe that many of our towers have capacity for additional tenants and that substantially all of our towers that are currently at or near full structural capacity can be upgraded or augmented to meet future tenant demand with relatively modest capital investment. Therefore, we will continue to target our sales and marketing activities to increase the utilization and return on investment of our existing communications sites.

Capital Allocation Strategy

As aThe objective of our capital allocation strategy is to simultaneously increase adjusted funds from operations and our return on invested capital. To maintain our REIT status we must annuallyare required to distribute to our stockholders annually an amount equal to at least 90% of our REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain), which is. After complying with our first priorityREIT distribution requirements, we plan to continue to allocate our available capital among investment alternatives that meet our return on investment criteria, while taking into account the repayment of debt to reduce our net leverage to be within our capital allocation strategy. After our REIT distributions,long-term target range. Accordingly, we expect to continue to deploy our discretionary capital through our annual discretionary capital expenditure program, including land purchases and new site construction and through acquisitions. The objective of our allocation of our discretionary capital is to simultaneously increase recurring free cash flow and our return on invested capital. In addition, we intend to return our remaining excess discretionary capital, if any, to stockholders through continuing our stock repurchase program or by declaring special distributions from time to time. During 2012,2013, we generated $1,414.4 million$1.6 billion of cash from operating activities, which along with incremental debt, was used to fund nearly $2,984.3 million$5.2 billion of investments, including $568.0 million of capital expenditures, $1,998.0 million$4.5 billion of acquisitions and $62.7$724.5 million of stock repurchases,

capital expenditures. In addition, in 2013, we repurchased $145.0 million, including commissions and fees. During 2012, wefees, of our common stock and paid regular cash distributions in the aggregate of approximately $355.6$434.7 million to our stockholders.

This includes capital expenditures associated with maintenance, increasing the capacity of our existing sites, and projects such as new site construction, land interest acquisitions and shared generator installations.

International Growth Strategy

We believe that, in certain international markets, we can create substantial value by either establishing ana new, or expanding our existing, independent wireless infrastructurereal estate leasing business. Therefore, we expect we will continue to seek international growth opportunities, where we believe our risk adjusted return objectives can be achieved. In addition, weWe strive to maintain a diversified approach to our international growth strategy by complementing our presence in emerging markets with operations in more developed and established markets.markets, which enables us to leverage multiple stages of wireless network development throughout our global footprint. Our international growth strategy includes a disciplined, individualized market evaluation, in which we conduct the following analyses:

Growth and ExpansionRecent Transactions

Acquisitions

In 2012,From January 1, 2013 through December 31, 2013, we continuedincreased our communications site portfolio by approximately 13,070 sites, including approximately 2,370 build-to-suits, and we believe the assets acquired will be accretive to focus on growing our operations using selective criteria for acquisitions, including expansion into new international markets, and new site development, consistent with our international growth strategy. Duringconsolidated operating margins. Acquisitions during the year ended December 31, 2012, we grew2013 included:

(November 2013) and approximately 1,940 communications sites in Brazil from NII (December 2013). These acquisitions strengthened our presence in our legacy markets by expanding our site portfolio by nearly 30% in Latin America.

We continue to evaluate potential complementary services to supplement our tower site growth and expansion strategy, as well as opportunities to acquire larger communications real estate portfolios that we believe we can effectively integrate into our existing business. For more information about our acquisitions, see note 6 to our consolidated financial statements included in this Annual Report.

United StatesFinancing Transactions. We continued to build on our established foundation in the United States, growing our domestic communications sites portfolio by 6% during

During the year ended December 31, 2012 primarily through2013, we raised capital, thereby increasing our financial flexibility and our ability to return value to our stockholders. Significant financing transactions in 2013 included those set forth below. For more information about our financing transactions, see Item 7 of this Annual Report under the acquisitioncaption “Management’s Discussion and constructionAnalysis of communications sitesFinancial Condition and Results of Operations—Liquidity and Capital Resources” and note 8 to our consolidated financial statements included in select locations throughout the country. Our expansion in

the United States during 2012 included the acquisition and construction of approximately 945 towers, the installation of approximately 15 in-building and outdoor DAS networks and the installation of approximately 600 shared generators on our sites.this Annual Report.

InternationalSecuritization. In March 2013, we completed a securitization transaction (the “Securitization”) involving assets related to 5,195 wireless and broadcast communications towers (the “Secured Towers”) owned by two of our special purpose subsidiaries, through a private offering of $1.8 billion of Secured Tower Revenue Securities, Series 2013-1A and Series 2013- 2A (collectively, the “Securities”). During 2012, we took additional stepsWe used the net proceeds from the Securitization to position ourselves for expansion into new international markets. After announcingrefinance the launch$1.75 billion of operations in Uganda at the end of 2011, we acquired approximately 960 towers through our joint venture during the first half of 2012. In addition, in November 2012, we announced that we had launched operations in Germany and subsequently completed the purchase of approximately 2,030 towersCommercial Mortgage Pass-Through Certificates, Series 2007-1 issued in the fourth quartersecuritization transaction completed in May 2007 (the “Certificates”).

Senior Notes Offerings.In January 2013, we completed a registered public offering of 2012, thereby expanding$1.0 billion aggregate principal amount of 3.50% senior unsecured notes due 2023 (the “3.50% Notes”). In August 2013, we completed a registered public offering of $750 million aggregate principal amount of 3.40% senior unsecured notes due 2019 (the “3.40% Notes”) and $500 million aggregate principal amount of 5.00% senior unsecured notes due 2024 (the “5.00% Notes”). We used the net proceeds from each of these notes offerings primarily to repay certain indebtedness under our international footprintexisting credit facilities.

Credit Facilities.We increased our borrowing capacity and financial flexibility by entering into a multi-currency $1.5 billion senior unsecured revolving credit facility in June 2013, which was subsequently increased to ten countries$2.0 billion (the “2013 Credit Facility”) and a 364-day $1.0 billion senior unsecured revolving credit facility in September 2013 (the “Short-Term Credit Facility”). As a result, as of December 31, 2012. Our international expansion efforts during 2012 also included2013, we had the acquisition and construction in the aggregate of approximately 4,855 towers and the installation of five in-building DAS networks inability to borrow up to $2.0 billion under our existing markets.credit facilities, net of any outstanding letters of credit. We also entered into a $1.5 billion unsecured term loan in October 2013 (the “2013 Term Loan”), and repaid our $750.0 million unsecured term loan entered into in June 2012 (the “2012 Term Loan”).

Regulatory Matters

Towers and Antennas. Our domestic and international tower business is subject to national, state and local regulatory requirements with respect to the registration, siting, construction, lighting, marking and maintenance of our towers. In the United States, which accounted for approximately 69%67% of our total rental and management

revenue for the year ended December 31, 2012,2013, the construction of new towers or modifications to existing towers may require pre-approval by the Federal Communications Commission (“FCC”) and the Federal Aviation Administration (“FAA”), depending on factors such as tower height and proximity to public airfields. Towers requiring pre-approval must be registered with the FCC and painted, lighted and maintained in accordance with FAA standards. Similar requirements regarding pre-approval of the construction and modification of towers are imposed by regulators in other countries. Non-compliance with applicable tower-related requirements may lead to monetary penalties or site deconstruction orders.

Furthermore, in India, each of our subsidiaries holds an Infrastructure Provider Category-I license (“IP-I”) issued by the Indian Ministry of Communications and Information Technology, which permits us to provide tower space to companies licensed as telecommunications service providers under the Indian Telegraph Act of 1885. While we are required to provide tower space on a non-discriminatory basis, we may negotiate mutually agreeable terms and conditions with such service providers. As a condition to the IP-I, the Indian government has the right to take over telecommunications infrastructure in the case of emergency or war. In Ghana, our subsidiary holds a Communications Infrastructure License, issued by the National Communications Authority (“NCA”), which permits us to establish and maintain passive telecommunications infrastructure services and DAS networks for communications service providers licensed by the NCA. While we are required to provide tower space on a non-discriminatory basis, we may negotiate mutually agreeable terms and conditions with such service providers. In Chile, our subsidiary is classified as a Telecom Intermediate Service Provider. We have received a number of site specific concessions and are working with the Chilean Subsecretaria de Telecommunicaciones to receive concessions on our remaining sites in Chile.

Our international business operations may be subject to increased licensing fees or ownership restrictions. For example, the Telecom Regulatory Authority of India has recommended to the Indian Department of Telecommunications changes in annual licensing fees for tower companies based on revenues generated, as well as the potential implementation of certain limitations on foreign ownership. To date, such changes have not been formally adopted. In South Africa, the Broad-Based Black Economic Empowerment Act, 2003 (“the BBBEE(the “BBBEE Act”) has established a legislative framework for the promotion of economic empowerment of South African citizens disadvantaged by Apartheid, and accordingly, the BBBEE Act and related codes measure BBBEE Act compliance and good corporate practice by the inclusion of certain ownership, management control, employment equity and other metrics for companies that do business there. Certain municipalities in Brazil and India have sought to impose certain permit fees based upon structural or operational requirements of towers. In addition, our foreign operations may be affected if a country’s regulatory authority restricts or revokes spectrum licenses of certain wireless service providers.

In all countries where we operate, we are subject to zoning restrictions and restrictive covenants imposed by local authorities or community organizations. TheseWhile these regulations vary, butthey typically require tower owners and/or our tenants to obtain approval from local authorities or community standards organizations prior to tower

construction or the addition of a new antenna to an existing tower. Local zoning authorities and community residents often oppose construction in their communities, which can delay or prevent new tower construction, new antenna installation or site upgrade projects, thereby limiting our ability to respond to customertenant demand. In addition, zoning regulations can increase costs associated with new tower construction, tower modifications, and additions of new antennas to a site or site upgrades. For instance, in June 2012, the Chilean government passed legislation retroactively imposing certain zoning restrictions on telecommunications towers, in response to which we developed a remediation plan. Existing regulatory policies may adversely affect the associated timing or cost of such projects and additional regulations may be adopted that cause delays or result in additional costs to us. These factors could materially and adversely affect our construction activities and operations. In the United States, the Telecommunications Act of 1996 prohibits any action by state and local authorities that would discriminate between different providers of wireless services or ban altogether the construction, modification or placement of communications sites. It also prohibits state or local restrictions based on the environmental effects of radio frequency emissions to the extent the facilities comply with FCC regulations. Further, in February 2012, the United States government adopted new regulations requiring that local and state governments approve modifications or collocations that qualify as eligible facilities under the regulations. In June 2012, the Chilean government passed a new law that imposes certain zoning restrictions retroactively on telecommunications towers located throughout Chile and may require us to modify or remove certain of our existing towers.

Portions of our business are subject to additional regulations, for example, in a number of states throughout the United States, certain of our subsidiaries hold Competitive Local Exchange Carrier (CLEC) status, or other similar status, in connection with the operation of our outdoor DAS networks business. In addition, we or our tenants, both domestic and international tenants may be subject to new regulatory policies in certain jurisdictions from time to time that may materially and adversely affect our business or the demand for our communications sites.

Environmental Matters. Our domestic and international operations like those of other companies engaged in similar businesses, are subject to various national, state and local environmental laws and regulations, including those relating to the management, use, storage, disposal, emission and remediation of, and exposure to, hazardous and non-hazardous substances, materials and wastes and the siting of our towers. As an owner, lessee and/or operator of real property and facilities, we may have liability under environmental laws for the costs of investigation, removal or remediation of soil and groundwater contaminated by hazardous substances or waste. Certain of these laws impose cleanup responsibility and liability without regard to whether we, as the owner, lessee or operator, knew of, or were responsible for, the contamination, and whether or not we have discontinued operations or sold the property. We also may be subject to common law claims by third parties based on damages and costs resulting from off-site migration of contamination. We may be required to obtain permits, pay additional property taxes, comply with regulatory requirements and make certain informational filings related to hazardous substances or devices used to provide power such as batteries, generators and fuel at our sites. Violations of these types of regulations could subject us to fines or criminal sanctions.

Additionally, in the United States and many other international markets where we do business, before constructing a new tower or adding a newan antenna to an existing site, we must review and evaluate the impact of the action to determine whether it may significantly affect the environment and whether we must disclose any significant impacts in an environmental assessment. If a tower or new antenna might have a material adverse impact on the environment, FCC or other governmental approval of the tower or antenna could be significantly delayed.

Health and Safety. In the United States and in other countries where we operate, we are subject to various national, state and local laws regarding employee health and safety, including protection from radio frequency exposure.

Competition

Our rental and management segmentsWe compete, both for new business and for the acquisition of assets, with other public tower companies, such as Crown Castle International Corp., SBA Communications Corporation and GTL Infrastructure, wireless carrier tower consortiums such as Indus Towers and private tower companies,

independent wireless carriers, tower owners, broadcasters and owners of non-communications sites, including rooftops, utility towers, water towers and other alternative structures. We believe that site location and capacity, network density, price, quality and speed of service have been, and will continue to be, significant competitive factors affecting owners, operators and managers of communications sites.

Our network development services segmentbusiness competes with a variety of companies offering individual, or combinations of, competing services. The field of competitors includes site acquisition consultants, zoning consultants, real estate firms, right-of-way consultants, structural engineering firms, tower owners/managers, telecommunications equipment vendors who can provide turnkey site development services through multiple subcontractors and our tenants’ internal staffs.personnel. We believe that our tenants base their decisions for network development services on various criteria, including a company’s experience, local reputation, price and time for completion of a project.

Customer Demand

Our strategy is predicated on ourthe belief that wireless service providers will continue to invest in the coverage, quality and capacity of their networks in both our domestic and international markets, driving demand for our communications sites.

As these factors continue to grow as a competitive necessityconsumer demand for and use of advanced wireless services in the United States on a widespread basis,grow, wireless service providers may be compelled to deploy new technology and equipment, further increase the cell density of their existing networks and expand their network coverage.

We believe demand for our communications sites will continue as wireless service providers seek to increase the quality, coverage area and capacity of their existing networks, while also investing in next generation data networks. To meet these network objectives, we believe wireless carriers will continue to outsource their communications site infrastructure needs as a means to accelerate access to their marketsnetwork development and more efficiently use their capital, rather than construct and operate their own communications sites and maintain

their own communications site operation and development capabilities. In addition, because our network development services are complementary to our rental and management business, we believe demand for our network development services will continue, consistent with industry trends.

Our customer demand could be adversely affected by the emergence and growth of new technologies, which could make it possible for wireless carriers to increase the capacity and efficiency of their existing networks.networks without the need for incremental cell sites. The increased use of spectrally efficient technologies and/or the availability of significant incremental spectrum in the marketplace could potentially relieve a portion of our tenants’ network capacity problems, and as a result, could reduce the demand for tower-based antenna space. Additionally, certain complementary network technologies, such as small cell deployments, could shift a portion of our tenants’ network investmentinvestments away from the traditional tower-based networks, which may reduce the need for carriers to add more equipment at certain communications sites.

In addition, any increase in the use of network sharing, roaming or resale arrangements by wireless service providers could adversely affect customer demand for tower space. These arrangements enable a provider to serve its customers outside itsthe provider’s license area, to give licensed providers the right to enter into arrangements to serve overlapping license areas and to permit non-licensed providers to enter the wireless marketplace. Consolidation among wireless carriers could similarly impact customer demand for our communications sites because the existing networks of wireless carriers often overlap. In addition, if wireless carriers sharesharing their sites or permitpermitting equipment location swapping on their sites with other carriers to a significant degree it could reduce demand for our communications sites. Further, our tenants may be subject to new regulatory policies from time to time that may materially and adversely affect the demand for our communications sites.

Employees

As of December 31, 2012,2013, we employed 2,4322,716 full-time individuals and consider our employee relations to be satisfactory.

Available Information

Our Internet website address iswww.americantower.com. Information contained on our website is not incorporated by reference into this Annual Report, and you should not consider information contained on our website as part of this Annual Report. You may access, free of charge, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, plus amendments to such reports as filed or furnished pursuant to Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (“Exchange Act”), through the “Investors”“Investor Relations” portion of our website as soon as reasonably practicable after we electronically file such material with, or furnish it to, the Securities and Exchange Commission (“SEC”).

We have adopted a written Code of Ethics and Business Conduct Policy (“Code(the “Code of Conduct”) that applies to all of our employees and directors, including, but not limited to, our principal executive officer, principal financial officer and principal accounting officer or controller or persons performing similar functions. The Code of Conduct, our corporate governance guidelines and the charters of the audit, compensation and nominating and corporate governance committees of our Board of Directors are available at the “Investors”“Investor Relations” portion of our website. In the event we amend the provisions of our Code of Conduct, or provide any waivers under the Code of Conduct forto our directors or executive officers, we intend towill disclose these events on our website as required by the regulations of the New York Stock Exchange (the “NYSE”) and applicable law.

In addition, paper copies of these documents may be obtained free of charge by writing us at the following address: 116 Huntington Avenue, Boston, Massachusetts 02116, Attention: Investor Relations; or by calling us at (617) 375-7500.

ITEM 1A.

RISK FACTORS

Decrease in demand for our communications sites would materially and adversely affect our operating results, and we cannot control that demand.

Factors affecting the demand for our communications sites and, to a lesser extent, our network development services, could materially and adversely affect our operating results. Those factors include:

Any downturn in the economy or disruption in the financial and credit markets could impact consumer demand for wireless services. If wireless service subscribers significantly reduce their minutes of use, or fail to

widely adopt and use wireless data applications, our wireless service provider tenants could experience a decrease in demand for their services. As a result, theyour tenants may scale back their capital expenditure plans, which could materially and adversely affect leasing demand for our communications sites and our network development services business, which could have a material adverse effect on our business, results of operations or financial condition.

Furthermore, the demand for broadcast space in the United States and Mexico depends on the needs of television and radio broadcasters. Among other things, technological advances, including the development of satellite-delivered radio and video services, may reduce the need for tower-based broadcast transmission. In addition, any significant increase in attrition rate or decrease in overall demand for broadcast space could have a material adverse effect on our business, results of operations or financial condition.

New technologiesIf our tenants share site infrastructure to a significant degree or changes in a tenant’s business modelconsolidate or merge, our growth, revenue and ability to generate positive cash flows could makebe materially and adversely affected.

Extensive sharing of site infrastructure, roaming or resale arrangements among wireless service providers as an alternative to leasing our tower leasing business less desirable andcommunications sites may cause new lease activity to slow if carriers utilize shared equipment rather than deploy new equipment, or may result in decreasing revenues.

The development and implementationthe decommissioning of new technologies designed to enhanceequipment on certain existing sites because portions of the efficiency of wirelesstenants’ networks or changes in a tenant’s business model could reduce the need for tower-based wireless services, decrease demand for tower space or reduce obtainable lease rates.may become redundant. In addition, significant consolidation among our tenants may materially adversely affect our growth and revenues. For example, in the United States, recently combined companies have lesseither rationalized or announced plans to rationalize duplicative parts of their budget allocated to lease space on our towers, as the industry is trending towards deploying increased capital to the development and implementation of new technologies. Examples of these technologies include spectrally efficient technologies which could relieve a portion of our tenants’ network capacity needs and as a result, could reduce the demand for tower-based antenna space. Additionally, certain small cell complementary network technologies could shift a portion of our tenants’ network investment away from the traditional tower-based networks, which may reduceresult in the need for carriers to add moredecommissioning of certain equipment at certainon our communications sites. Moreover, the emergenceWe would expect a similar outcome in certain other countries where we do business if consolidation of alternative technologiescertain tenants occurs. In addition, certain combined companies have modernized or are currently modernizing their networks, and these and other tenants could reduce the need for tower-based broadcast services transmissiondetermine not to renew leases with us as a result. Our ongoing contractual revenues and reception. For example, the growth in delivery of wireless communications, radio and video services by direct broadcast satellites could materially and adversely affect demand for our tower space. Further,

future results may be negatively impacted if a tenant may decide to no longer outsource tower infrastructure or otherwise change its business model which would result in a decrease in our revenue. The development and implementation of anysignificant number of these and similar technologies to any significant degree or changes in a tenant’s business model could have a material adverse effect on our business, results of operations or financial condition.leases are not renewed.

Our business is subject to government regulations and changes in current or future laws or regulations could restrict our ability to operate our business as we currently do.

Our business and that of our tenants are subject to federal, state, local and foreign regulations. In certain jurisdictions, these regulations could be applied or enforced retroactively. Local zoningZoning authorities and community organizations are often opposed to the construction of communications sites in their communities, and these regulationswhich can delay, prevent or increase the cost of new tower construction, modifications, additions of new antennas to a site or site upgrades, thereby limiting our ability to respond to tenant demands and requirements. In addition, in certain foreign jurisdictions, we are required to pay annual license fees, and these fees may be subject to substantial increases by the government. Foreign jurisdictions in which we operate and currently are not required to pay license fees may enact license fees, which may apply retroactively. In certain foreign jurisdictions, there may be changes to zoning regulations or construction laws based on site location which may result in increased costs to modify certain of our existing towers or decreased revenue due to the removal of certain towers to ensure compliance with such changes. Existing regulatory policies may materially and adversely affect the associated timing or cost of such projects and additional regulations may be adopted that increase delays or result in additional costs to us, or that prevent such projects in certain locations. Furthermore, the tax laws, regulations and interpretations governing REITs may change at any time. These factors could materially and adversely affect our business, results of operations or financial condition.

If our tenants consolidate, merge or share site infrastructure with each other to a significant degree, our growth, revenueOur leverage and ability to generate positive cash flows could bedebt service obligations may materially and adversely affected.affect us.

Significant consolidation amongAs of December 31, 2013, we had approximately $14.5 billion of consolidated debt and the ability to borrow additional amounts of approximately $2.0 billion under our tenants may result incredit facilities, net of any outstanding letters of credit. Our leverage could render us unable to generate cash sufficient to pay when due the decommissioningprincipal of, certain existing communications sites, because certain portions of these tenants’ networks may be redundant. For example, in the United States, recently combined companies have either rationalized or announced plans to rationalize duplicative parts of their networks, which may result in the decommissioning of certain equipment

interest on, our communications sites. We would expect a similar outcome in certain other countries where we do business if consolidation of certain tenants occurs. In addition, certain combined companies have undergone or are currently undergoing a modernization of their networks, and these and other tenants could determine not to renew leases with us as a result. Our ongoing contractual revenues and our future results may be negatively impacted if a significant number of these leases are not renewed. Similar consequences might occur if wireless service providers engage in extensive sharing of site infrastructure, roaming or resale arrangements as an alternative to leasing our communications sites.

We could suffer adverse tax or other financial consequences if taxing authorities do not agree with our tax positions.

We periodically are subject to examinations by taxing authorities in the states and countries where we do business, and we expect that we will continue to be subject to tax examinations in the future. Moreover, the Internal Revenue Service and any state or local tax authority may successfully assert liabilities against us for corporate income taxes for taxable years prior to the time we qualified as a REIT, oramounts due with respect to, our TRSs,indebtedness. We are also permitted, subject to certain restrictions under our existing indebtedness, to draw down on our credit facilities and obtain additional long-term debt and working capital lines of credit to meet future financing needs.

Our leverage could have significant negative consequences on our business, results of operations or financial condition, including:

In addition, to meet the REIT distribution requirements and maintain our qualification and taxation as a REIT, will increase and we may be requiredneed to pay deficiency dividendsborrow funds, even if the then-prevailing market conditions are not favorable, and an associated interest charge ifthe REIT distribution requirements may increase the financing we need to fund capital expenditures, future growth and expansion initiatives. This would increase our prior REIT distributions were insufficienttotal leverage.

Increasing competition in lightthe tower industry may materially and adversely affect us.

We may experience increased competition, which could make the acquisition of the reduced available NOLs.

Our industry is highly competitive and our tenants have numerous alternatives in leasing antenna space. Competitive pricing for tenants on towers from competitors could materially and adversely affect our lease rates and services income. In addition, domestic and international tax laws and regulations are extremely complex and subject to varying interpretations. We recognize tax benefits of uncertain tax positions when we believe the positions are more likely than not to be sustained upon a challenge by the relevant tax authority. We believe our judgments in this area are reasonable and correct, but there is no guarantee that our tax positions willmay not be challenged by relevant tax authoritiesable to renew existing tenant leases or that we would be successful in any such challenge. If there are tax benefits that are challenged successfully by a taxing authority, we may be required to pay additional taxes or use our NOLs or we may seek to enter into settlements with the taxing authorities, all of which could require significant payments or otherwise havenew tenant leases, resulting in a material adverse effectimpact on our results of operations and growth rate.

The higher prices for assets, combined with the competitive pricing pressure on tenant leases, could make it more difficult to achieve our return on investment criteria. Increasing competition for either tower assets or tenants could materially and adversely affect our business, results of operations or financial condition.

Our expansion initiatives involve a number of risks and uncertainties that could adversely affect our operating results, disrupt our operations or expose us to additional risk if we are not able to successfully integrate operations, assets and personnel.

As we continue to acquire communications sites in our existing markets and expand into new markets, we are subject to a number of risks and uncertainties, including not meeting our return on investment criteria and

financial objectives, increased costs, assumed liabilities and the diversion of managerial attention due to acquisitions. Achieving the benefits of acquisitions depends in part on timely and efficiently integrating operations, communications tower portfolios and personnel. Integration may be difficult and unpredictable for many reasons, including, among other things, differing systems and processes, cultural differences, customary business practices and conflicting policies, procedures and operations. In addition, integrating businesses may significantly burden management and internal resources, including the potential loss or unavailability of key personnel.

Furthermore, our international expansion initiatives are subject to additional risks such as complex laws, regulations and business practices that may require additional resources and personnel, and the other risks described immediately below in “—Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.” As a result, our foreign operations and expansion initiatives may not succeed and may materially and adversely affect our business, results of operations or financial condition.

Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.

Our international business operations and our expansion into new markets in the future could result in adverse financial consequences and operational problems not typically experienced in the United States. For the year ended December 31, 2013, approximately 33% of our consolidated revenue was generated by our international operations, compared to 30% for the year ended December 31, 2012. We anticipate that our revenues from our international operations will continue to grow. Accordingly, our business is subject to risks associated with doing business internationally, including:

We also face risks associated with changes in foreign currency exchange rates, including those arising from our operations, investments and financing transactions related to our international business. Volatility in foreign currency exchange rates can also affect our ability to plan, forecast and budget for our international operations and expansion efforts. Our revenues earned from our international operations are primarily denominated in their respective local currencies. We have not historically engaged in significant currency hedging activities relating to our non-U.S. Dollar operations, and a weakening of these foreign currencies against the U.S. Dollar would negatively impact our reported revenues, operating profits and income.

In our international operations, many of our tenants are subsidiaries of global telecommunications companies. These subsidiaries may not have the explicit or implied financial support of their parent entities.

In addition, as we continue to invest in joint venture opportunities internationally, our partners may have business or economic goals that are inconsistent with ours, be in positions to take action contrary to our interests, policies or objectives, have competing interests in our, or other, markets that could create conflict of interest issues, withhold consents contrary to our requests or become unable or unwilling to fulfill their commitments, any of which could expose us to additional liabilities or costs, including requiring us to assume and fulfill the obligations of that joint venture.

A substantial portion of our revenue is derived from a small number of tenants, and we are sensitive to changes in the creditworthiness and financial strength of our tenants.

A substantial portion of our total operating revenues is derived from a small number of tenants. For the year ended December 31, 2012,2013, four tenants accounted for approximately 74%83% of our domestic rental and management segment revenue; and five tenants accounted for approximately 55% of our international rental and management segment revenue. If any of these tenants areis unwilling or unable to perform theirits obligations under our agreements with them,it, our revenues, results of operations, financial condition and liquidity could be materially and adversely affected. In the ordinary course of our business, we do occasionally experience disputes with our tenants, generally regarding the interpretation of terms in our leases. We have historically resolved these disputes in a manner that did not have a material adverse effect on us or our tenant relationships. However, it is possible that such disputes could lead to a termination of our leases with tenants or a material modification of the terms of those leases, either of which could have a material adverse effect on our business, results of operations or financial condition. If we are forced to resolve any of these disputes through litigation, our relationship with the applicable tenant could be terminated or damaged, which could lead to decreased revenuesrevenue or increased costs, resulting in a corresponding adverse effect on our business, results of operations or financial condition.

Additionally, due to the long-term nature of our tenant leases, we depend on the continued financial strength of our tenants. Many wireless service providers operate with substantial leverage. Some ofSometimes our tenants may experienceface financial difficulty or may file for bankruptcy. In addition, many of our tenants and potential tenants rely on capital raising activities to fund their operations and capital expenditures. Downturns in the economy and disruptions in the financial and credit markets have periodically made it more difficult and more expensive to raise capital. If our tenants or potential tenants are unable to raise adequate capital to fund their business plans, they may reduce their spending, which could materially and adversely affect demand for our communications sites and our network development services business. If, as a result of a prolonged economic downturn or otherwise, one or more of our significant tenants experienced financial difficulties or filed for bankruptcy, it could result in uncollectible accounts receivable and an impairment of our deferred rent asset, tower asset, network location intangible asset or customer-related intangible asset. The loss of significant tenants, or the loss of all or a portion of our anticipated lease revenues from certain tenants, could have a material adverse effect on our business, results of operations or financial condition.

Our foreignWe may fail to realize the growth prospects and cost savings anticipated as a result of, and will incur significant transaction and acquisition-related integration costs in connection with, our acquisition of MIPT.

The success of the acquisition of MIPT will depend, in part, on our ability to realize the anticipated business opportunities and growth prospects from combining our business with those of MIPT. We may never realize

these business opportunities and growth prospects, or we may encounter unanticipated accounting, internal control, regulatory or compliance problems.

In addition, we and MIPT have operated independently. As a result, there may be a disruption of each company’s ongoing businesses, tax costs or inefficiencies, or inconsistencies in standards, controls, information technology systems, procedures and policies, any of which could adversely affect our ability to maintain relationships with tenants, employees or other third parties or our ability to achieve the anticipated benefits of the acquisition and could harm our financial performance. We anticipate that we will incur certain non-recurring charges in connection with integrating MIPT, including severance and charges associated with integrating process and systems. We currently cannot identify the timing, nature and amount of all such charges. Further, the significant acquisition-related integration costs could materially adversely affect our results of operations in the period in which such charges are subjectrecorded or our cash flow in the period in which any related costs are actually paid. Although we believe that the elimination of duplicative costs, as well as the realization of other efficiencies related to economic, politicalthis integration, will offset incremental transaction and other risksacquisition-related costs over time, this net benefit may not be achieved in the near term, or at all. We also expect to incur costs to implement such efficiencies. In that regard, because MIPT is a private company, we may be required to improve MIPT’s internal controls, procedures and policies to meet standards applicable to public companies, which may be time-consuming and more expensive than anticipated.

New technologies or changes in a tenant’s business model could make our tower leasing business less desirable and result in decreasing revenues.

The development and implementation of new technologies designed to enhance the efficiency of wireless networks or changes in a tenant’s business model could reduce the need for tower-based wireless services, decrease demand for tower space or reduce previously obtainable lease rates. In addition, tenants may have less of their budgets allocated to lease space on our towers, as the industry is trending towards deploying increased capital to the development and implementation of new technologies. Examples of these technologies include spectrally efficient technologies, which could relieve a portion of our tenants’ network capacity needs and as a result, could reduce the demand for tower-based antenna space. Additionally, certain small cell complementary network technologies could shift a portion of our tenants’ network investments away from the traditional tower-based networks, which may reduce the need for carriers to add more equipment at certain communications sites. Moreover, the emergence of alternative technologies could reduce the need for tower-based broadcast services transmission and reception. For example, the growth in the delivery of wireless communications, radio and video services by direct broadcast satellites could materially and adversely affect demand for our revenuestower space. Further, a tenant may decide to no longer outsource tower infrastructure or financial position, including risks associated with fluctuations in foreign currency exchange rates.

Our internationalotherwise change its business operations and our expansion into new markets in the future couldmodel, which would result in adverse financial consequencesa decrease in our revenue. The development and operational problems not typically experienced in the United States. For the year ended December 31, 2012, approximately 30%implementation of our consolidated revenue was generated by our international operations, comparedany of these and similar technologies to 26% for the year ended December 31, 2011. We anticipate that our revenues from our international operations will continue to grow. Accordingly, our business is subject to risks associated with doing business internationally, including:

In our international operations, many of our tenants are subsidiaries of global telecommunications companies. These subsidiaries may not have the explicit or implied financial support of their parent entities.

In addition, as we continue to invest in joint venture opportunities internationally, our partners may have business or economic goals that are inconsistent with ours, be in positions to take action contrary to our interests, policies or objectives, have competing interests in our markets that could create conflict of interest issues, withhold consents contrary to our requests or become unable or unwilling to fulfill their commitments, which could expose us to additional liabilities or costs, including requiring us to assume and fulfill the obligations of that joint venture.

We also face risks associated with changes in foreign currency exchange rates, including those arising from our operations, investments and financing transactions related to our international business. Volatility in foreign currency exchange rates can also affect our ability to plan, forecast and budget for our international operations and expansion efforts. Our revenues earned from our international operations are primarily denominated in their respective local currencies. We have not historically engaged in significant currency hedging activities relating to our non-U.S. Dollar operations, and a weakening of these foreign currencies against the U.S. Dollar would have a negative impactmaterial adverse effect on our reported revenues, operating profits and income.

Our expansion initiatives involve a number of risks and uncertainties that could adversely affect our operating results, disrupt our operations or expose us to additional risk if we are not able to successfully integrate operations, assets and personnel.

As we continue to acquire communications sites in our existing markets and expand into new markets, we are subject to a number of risks and uncertainties, including not meeting our return on investment criteria and financial objectives, increased costs, assumed liabilities and the diversion of managerial attention due to acquisitions. Achieving the benefits of acquisitions depends in part on integrating operations, communications tower portfolios and personnel in a timely and efficient manner. Integration may be difficult and unpredictable for many reasons, including, among other things, differing systems and processes, potential cultural differences, customary business practices and conflicting policies, procedures and operations. In addition, the integration of businesses may significantly burden management and internal resources, including the potential loss or unavailability of key personnel.

Furthermore, our international expansion initiatives are subject to additional risks such as complex laws, regulations and business practices that may require additional resources and personnel, and the other risks

described above in “—Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.” As a result, our foreign operations and expansion initiatives may not succeed and may materially and adversely affect our business, results of operations or financial condition.

If we fail to remain qualified as a REIT, we will be subject to tax at corporate income tax rates, which may substantially reduce funds otherwise available.

Effective for the taxable year beginning January 1, 2012, we began operating as a REIT for federal income tax purposes. If we fail to remain qualified as a REIT, we will be taxed at corporate income tax rates unless certain relief provisions apply.

Qualification as a REIT requires application of certain highly technical and complex provisions of the Internal Revenue Code of 1986, as amended (the “Code”), which provisions may change from time to time, to our operations as well as various factual determinations concerning matters and circumstances not entirely within our control. There are limited judicial or administrative interpretations of the relevant provisions of the Code.

If, in any taxable year, we fail to qualify for taxation as a REIT, and are not entitled to relief under the Code:

Any corporate tax liability could be substantial and would reduce the amount of cash available for other purposes. If we fail to qualify for taxation as a REIT, we may need to borrow additional funds or liquidate some investments to pay any additional tax liability. Accordingly, funds available for investment and operations would be reduced.

Furthermore, as a result of our acquisition of MIPT, we own an interest in a subsidiary REIT. The subsidiary REIT is independently subject to, and must comply with, the same REIT requirements that we must satisfy in order to qualify as a REIT, together with all other rules applicable to REITs. If the subsidiary REIT fails to qualify as a REIT, and certain relief provisions do not apply, then (i) the subsidiary REIT would become subject to federal income tax, (ii) the subsidiary REIT will be disqualified from treatment as a REIT for the four taxable years immediately following the year during which qualification was lost, (iii) our ownership of shares in such subsidiary REIT will cease to be a qualifying asset for purposes of the asset tests applicable to REITs and any dividend income or gains derived by us from such subsidiary REIT may cease to be treated as income that qualifies for purposes of the 75% gross income test and (iv) we may fail certain of the asset tests applicable to REITs, in which event we will fail to qualify as a REIT unless we are able to avail ourselves of certain relief provisions.

We may be limited in our ability to fund required distributions using cash generated through our TRSs.

As a REIT, we must distribute to our stockholders an amount equal to at least 90% of the REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Our ability to receive distributions from our TRSs to fund these distributions is limited by the rules with which we must comply to maintain our status as a REIT. In particular, at least 75% of our gross income for each taxable year as a REIT must be derived from real estate, which principally includes gross income from the leasing of our communications sites and qualified rental-related services. Consequently, no more than 25% of our gross income may consist of dividend income from our TRSs and other non-qualifying types of income. Thus, our ability to receive distributions from our TRSs may be limited and may impact our ability to fund distributions to our stockholders.

In addition, the majority of our income and cash flows from our TRSs are generated from our international operations. In many cases, there are local withholding taxes and currency controls that may impact our ability or willingness to repatriate funds to the United States to help satisfy REIT distribution requirements.

Complying with REIT requirements may limit our flexibility or cause us to forego otherwise attractive opportunities.

Our use of TRSs enables us to engage in non-REIT qualifying business activities. Under the Code, no more than 25% of the value of the assets of a REIT may be represented by securities of one or more TRSs and other non-qualifying assets. This limitation may hinder our ability to make certain attractive investments, including the purchase of non-qualifying assets, the expansion of non-real estate activities, and investments in the businesses to be conducted by our TRSs, and to that extent limit our opportunities and our flexibility to change our business strategy.

Specifically, this limitation may affect our ability to make additional investments in our managed networks business or network development services segment as currently structured and operated, in other non-REIT qualifying operations or assets, or in international operations conducted through TRSs that we do not elect to bring into the REIT structure. Further, acquisition opportunities in domestic and international markets may be

adversely affected if we need or require the target company to comply with certain REIT requirements prior to closing.

In addition, to meet our annual distribution requirements, we may be required to distribute amounts that may otherwise be used for our operations, including amounts that may otherwise be invested in future acquisitions, capital expenditures or repayment of debt, and it is possible that we might be required to borrow funds, sell assets or raise equity to fund these distributions, even if the then-prevailing market conditions are not favorable for these borrowings, sales or offerings.

Certain of our business activities may be subject to corporate level income tax and foreign taxes, which reduce our cash flows, and may create deferred and contingent tax liabilities.

We are subject to certain federal, state, local and foreign taxes on our income and assets, including alternative minimum taxes, taxes on any undistributed income and state, local or foreign income, franchise, property and transfer taxes. Any of these taxes would decrease our earnings and our available cash.

Our TRS assets and operations will continue to be subject, as applicable, to federal and state corporate income taxes and to foreign taxes in the jurisdictions in which those assets and operations are located.

We may need additional financing to fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements.

To fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements, we may need to raise additional capital through financing activities, sell assets or raise equity. We believe our cash provided by operations for the year ending December 31, 2014 will sufficiently fund our cash needs for operations, capital expenditures, required REIT distribution payments and cash debt service (interest and principal repayments) obligations through 2014. However, we anticipate that we may need to obtain additional sources of capital in the future to fund capital expenditures, future growth and expansion initiatives and satisfy our REIT distribution requirements. Depending on market conditions, we may seek to raise capital through credit facilities or debt or equity offerings. An increase in our outstanding debt could lead to a downgrade of our credit rating. A downgrade of our credit rating below investment grade could negatively impact our ability to access credit markets or preclude us from obtaining funds on investment grade terms and conditions. Further, certain of our current debt instruments limit the amount of indebtedness we and our subsidiaries may incur. Additional financing, therefore, may be unavailable, more expensive or restricted by the terms of our outstanding indebtedness. If we are unable to raise capital when our needs arise, we may not be able to fund our capital expenditures, future growth and expansion initiatives or satisfy our REIT distribution requirements.

If we are unable to protect our rights to the land under our towers, it could adversely affect our business and operating results.

Our real property interests relating to our towers consist primarily of leasehold and sub-leasehold interests, fee interests, easements, licenses and rights-of-way. A loss of these interests at a particular tower site may interfere with our ability to operate a tower and generate revenues. For various reasons, we may not always have the ability to access, analyze and verify all information regarding titles and other issues prior to completing an acquisition of communications sites, which can affect our rights to access and operate a site. From time to time we also experience disputes with landowners regarding the terms of ground agreements for land under a tower,towers, which can affect our ability to access and operate a tower site.sites. Further, for various reasons, landowners may not want to renew their ground agreements with us, they may lose their rights to the land, or they may transfer their land interests to third parties, including ground lease aggregators, which could affect our ability to renew ground agreements on commercially viable terms. Approximately 88% of the communications sites in our portfolio as of December 31, 20122013 are located on land we lease pursuant to operating leases. Approximately 78%74% of the ground

leases for these sites have a final expiration date of 20222023 and beyond. Further, for various reasons, title to property interests in some of the foreign jurisdictions in which we operate may not be as certain as title to our property interests in the United States. Our inability to protect our rights to the land under our towers may have a material adverse effect on our business, results of operations or financial condition.

Increasing competition in the tower industry may create pricing pressures that may materially and adversely affect us.

Our industry is highly competitive and our tenants have numerous alternatives in leasing antenna space. Some of our competitors, such as wireless carriers that allow collocation on their towers, are larger and may have greater financial resources than we do, while other competitors may have lower return on investment criteria than we do.

Competitive pricing for tenants on towers from these competitors could materially and adversely affect our lease rates and services income, as well as require us to pay significantly more to acquire assets. In addition, we may not be able to renew existing tenant leases or enter into new tenant leases, resulting in a material adverse impact on our results of operations and growth rate. Increasing competition could also make the acquisition of high quality tower assets more costly. Any of these factors could materially and adversely affect our business, results of operations or financial condition.

If we are unable or choose not to exercise our rights to purchase towers that are subject to lease and sublease agreements at the end of the applicable period, our cash flows derived from such towers wouldwill be eliminated.

Our communications real estate portfolio includes towers that we operate pursuant to lease and sublease agreements that include a purchase option at the end of each lease period. We may not have the required available capital to exercise our right to purchase leased or subleased towers at the end of the applicable period. Even if we do have available capital,period, or we may choose, for business or other reasons not to exercise our right to purchase such towers for business or other reasons.towers. In the event that we do not exercise these purchase rights, or are otherwise unable to acquire an interest that would allow us to continue to operate these towers after the applicable period, we wouldwill lose the cash flows derived from such towers. In the event that we decide to exercise these purchase rights, the benefits of the acquisitions of a significant number of towers may not exceed the associated acquisition, compliance and integration costs, which could have a material adverse effect on our business, results of operations or financial condition.

If we fail to qualify as a REIT or fail to remain qualified as a REIT, we would be subject to tax at corporate income tax rates, which would substantially reduce funds otherwise available.

We began operating as a REIT for federal income tax purposes, effective for the taxable year beginning January 1, 2012. If we fail to qualify as a REIT, we will be taxed at corporate income tax rates unless certain relief provisions apply. We believe that we are organized and will qualify as a REIT upon timely filing our federal income tax return for 2012, and we intend to operate in a manner that will allow us to continue to qualify as a REIT. However, we cannot guarantee that we will qualify or remain so qualified, including if our Board of Directors determines it is no longer in our interests to be a REIT.

Qualification as a REIT requires application of certain highly technical and complex provisions of the Internal Revenue Code of 1986, as amended (the “Code”), which provisions may change from time to time, to our operations as well as various factual determinations concerning matters and circumstances not entirely within our control. There are limited judicial or administrative interpretations of the Code provisions.

For instance, the net income of our TRSs is not required to be distributed to us, and such undistributed TRS income is generally not subject to our REIT distribution requirements. However, if the accumulation of cash or reinvestment of significant earnings in our TRSs causes the fair market value of our securities in those entities, taken together with other non-qualifying assets, to exceed 25% of the fair market value of our assets, in each case as determined for REIT asset testing purposes, we would, absent timely responsive action, fail to qualify as a REIT.

If, in any taxable year, we fail to qualify for taxation as a REIT, and are not entitled to relief under the Code:

Any corporate tax liability could be substantial and would reduce the amount of cash available for other purposes. If we fail to qualify for taxation as a REIT, we may need to borrow additional funds or liquidate some investments to pay any additional tax liability. Accordingly, funds available for investment and operations would be reduced.

We may be limited in our ability to fund required distributions using cash generated through our TRSs.

As a REIT, we must distribute to our stockholders an amount equal to at least 90% of the REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Timing differences between the receipt of income and the recognition of income for federal income tax purposes, as well as the effect of non-deductible expenditures, may impair our ability to fund required distributions. If our cash available for distribution falls short of our estimates, we may be unable to maintain distributions that approximate our REIT taxable income, and as a result, may fail to qualify for taxation as a REIT. To the extent that we satisfy the 90% distribution requirement, but distribute less than 100% of our REIT taxable income, we will be subject to federal corporate income tax on our undistributed taxable income. In addition, we will be subject to a 4% nondeductible excise tax if the actual amount that we distribute to our stockholders for a calendar year is less than the minimum amount specified under the Code.

Our ability to receive distributions from our TRSs is limited by the rules with which we must comply to maintain our status as a REIT. In particular, at least 75% of our gross income for each taxable year as a REIT must be derived from real estate, which principally includes gross income from the leasing of our communications sites and rental-related services. Consequently, no more than 25% of our gross income may consist of dividend income from our TRSs and other non-qualifying types of income. Thus, our ability to receive

distributions from our TRSs may be limited, and may impact our ability to fund distributions to our stockholders. Specifically, if our TRSs become highly profitable, we might become limited in our ability to receive net income from our TRSs in an amount required to fund distributions to our stockholders commensurate with that profitability.

In addition, the majority of our income and cash flows from our TRSs are generated from our international operations. In many cases, there are local withholding taxes and currency controls that may impact our ability or willingness to repatriate funds to the United States to help satisfy REIT distribution requirements.

Complying with REIT requirements may limit our flexibility or cause us to forego otherwise attractive opportunities.

To qualify as a REIT for federal income tax purposes, we must continually satisfy tests concerning, among other things, the sources of our income, the nature and diversification of our assets, the amounts we distribute to our stockholders and the concentration of ownership of our stock. Compliance with these tests will require us to refrain from certain activities and may hinder our ability to make certain attractive investments, including the purchase of non-qualifying assets, the expansion of non-real estate activities, and investments in the businesses to be conducted by our TRSs, and to that extent limit our opportunities and our flexibility to change our business strategy. We could also be required to liquidate otherwise attractive investments, and could be limited in our ability to hedge liabilities and risks. Furthermore, acquisition opportunities in domestic and international markets may be adversely affected if we need or require the target company to comply with some REIT requirements prior to closing. In addition, we may receive pressure from investors not to pursue growth opportunities that are not immediately accretive.

Under the Code, no more than 25% of the value of the assets of a REIT may be represented by securities of one or more TRSs and other non-qualifying assets. This limitation may affect our ability to make additional investments in our managed networks business or network development services segment as currently structured and operated, in other non-REIT qualifying operations or assets, or in international operations conducted through TRSs that we do not elect to bring into the REIT structure. To meet our annual distribution requirements, we may be required to distribute amounts that may otherwise be used for our operations, including amounts that may otherwise be invested in future acquisitions, capital expenditures or repayment of debt, and it is possible that we might be required to borrow funds, sell assets or raise equity to fund these distributions, even if the then-prevailing market conditions are not favorable for these borrowings, sales or offerings.

Certain of our business activities may be subject to corporate level income tax and foreign taxes, which reduce our cash flows, and may have deferred and contingent tax liabilities.

We are subject to certain federal, state, local and foreign taxes on our income and assets, including alternative minimum taxes, taxes on any undistributed income and state, local or foreign income, franchise, property and transfer taxes. In addition, we could, in certain circumstances, be required to pay an excise or penalty tax, which could be significant in amount, in order to utilize one or more relief provisions under the Code to maintain qualification for taxation as a REIT. Any of these taxes would decrease our earnings and our available cash.

Our TRS assets and operations will continue to be subject, as applicable, to federal and state corporate income taxes and to foreign taxes in the jurisdictions in which those assets and operations are located.

We will also be subject to a federal corporate level tax at the highest regular corporate rate (currently 35%) on the gain recognized from a sale of assets occurring within a specified period (generally, ten years) after the REIT Conversion, up to the amount of the built-in gain that existed on January 1, 2012, which is based on the fair market value of those assets in excess of our tax basis as of January 1, 2012. Gain from a sale of an asset occurring after the specified period ends will not be subject to this corporate level tax. We currently do not

expect to sell any asset if the sale would result in the imposition of a material tax liability, but our plans may change in the future.

We may need additional financing to fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements.

To fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements, we may need to raise additional capital through financing activities, sell assets or raise equity. We believe our cash provided by operations for the year ending December 31, 2013 will sufficiently fund our cash needs for operations, capital expenditures, required REIT distribution payments and cash debt service (interest and principal repayments) obligations through 2013. However, we anticipate that we may need to obtain additional sources of capital in the future to fund capital expenditures, future growth and expansion initiatives and satisfy our REIT distribution requirements. Depending on market conditions, we may seek to raise capital through credit facilities or debt or equity offerings. Additionally, a downgrade of our credit rating below investment grade could negatively impact our ability to access credit markets or preclude us from obtaining funds on investment grade terms and conditions. Further, certain of our current debt instruments limit the amount of indebtedness we and our subsidiaries may incur. Additional financing, therefore, may be unavailable, more expensive or restricted by the terms of our outstanding indebtedness. If we are unable to raise capital when our needs arise, we may not be able to fund our capital expenditures, future growth and expansion initiatives or satisfy our REIT distribution requirements.

Our leverage and debt service obligations may materially and adversely affect us.

In order to meet the REIT distribution requirements and maintain our qualification and taxation as a REIT, we may need to borrow funds, sell assets or raise equity, even if the then-prevailing market conditions are not favorable for these borrowings, sales or offerings. Any insufficiency of our cash flows to cover our REIT distribution requirements could adversely impact our ability to raise short- and long-term debt, to sell assets or to offer equity securities. Furthermore, the REIT distribution requirements may increase the financing we need to fund capital expenditures, future growth and expansion initiatives. This would increase our total leverage.

As of December 31, 2012, we had approximately $8.8 billion of consolidated debt and the ability to borrow additional amounts of approximately $0.7 billion under our credit facilities. Our leverage could render us unable to generate cash sufficient to pay when due the principal of, interest on, or other amounts due with respect to our indebtedness. We are also permitted, subject to certain restrictions under our existing indebtedness, to draw down on our credit facilities and obtain additional long-term debt and working capital lines of credit to meet future financing needs.

Our leverage could have significant negative consequences on our business, results of operations or financial condition, including:

Restrictive covenants in the loan agreements related to our securitization transaction, the loan agreements fortransactions, our credit facilities and the indentures governing our debt securities could materially and adversely affect our business by limiting flexibility.

The loan agreementagreements related to our securitization transaction includestransactions include operating covenants and other restrictions customary for loans subject to rated securitizations. Among other things, the borrowers under the loan agreement for the securitization transactionagreements are prohibited from incurring other indebtedness for borrowed money or further encumbering their assets. A failure to comply with the covenants in the loan agreementagreements could prevent the borrowers from taking certain actions with respect to the towers subject to the securitization transactionsecured assets and could prevent the borrowers from distributing any excess cash from the operation of such towersassets to us. If the borrowers were to default on any of the loan,loans, the servicer on thesuch loan could seek to foreclose upon or otherwise convert the ownership of the towers subject to the securitization transaction,secured assets, in which case we could lose such towersassets and the excess cash flow associated with such towers.assets.

The loan agreements for our credit facilities contain restrictive covenants, as well as requirements to comply with certain leverage and other financial maintenance tests, and could thus limit our ability to take various actions, including incurring additional debt, guaranteeing indebtedness or making distributions to stockholders, and engaging in various types of transactions, including mergers, acquisitions and sales of assets. Additionally, our indenturesdebt agreements restrict our and our subsidiaries’ ability to incur liens securing our or their indebtedness. These covenants could have an adverse effect on our business by limiting our ability to take advantage of financing, new tower development, mergers and acquisitions or other opportunities. Further, if these limits prevent us from satisfying our REIT distribution requirements, we could fail to qualify for taxation as a REIT. If these limits do not jeopardize our qualification for taxation as a REIT but nevertheless prevent us from distributing 100% of our REIT taxable income, we wouldwill be subject to federal corporate income tax, and potentially a nondeductible excise tax, on the retained amounts.

In addition, reporting and information covenants in our loancredit agreements and indentures require that we provide financial and operating information within certain time periods. If we are unable to timely provide the required information, we would be in breach of these covenants. For more information regarding the covenants and requirements discussed above, please see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources—Factors Affecting Sources of Liquidity” and note 8 to our consolidated financial statements included in this Annual Report.

We may incur goodwill and other intangible asset impairment charges, which could result in a significant reduction to our earnings.

We reviewIn accordance with accounting principles generally accepted in the United States (“GAAP”), we are required to assess our goodwill and other intangible assets annually to determine if it is impaired or more frequently in the event of circumstances indicating potential impairment.impairment to determine if they are impaired. These circumstances could include a decline in our actual or expected future cash flows or income, a significant adverse change in the business climate, a decline in market capitalization, or slower growth rates in our industry, among others. If the testing performed indicates that impairment has occurred,an asset may not be recoverable, we are required to record a non-cash impairment charge for the difference between the carrying value of the goodwill or other intangible assets and the implied fair value of the goodwill or other intangible assets in the period the determination is made.

While we did not record any impairment charges during the year ended December 31, 2012, itIt is possible that in the future, we may be required to record impairment charges for our goodwill or for other intangible assets. These charges could be significant, which could have a material adverse effect on our business, results of operations or financial condition.

WeOur costs could increase and our revenues could decrease due to perceived health risks from radio emissions, especially if these perceived risks are substantiated.

Public perception of possible health risks associated with cellular and other wireless communications technology could slow the growth of wireless companies, which could in turn slow our growth. In particular, negative public perception of, and regulations regarding, these perceived health risks could undermine the market acceptance of wireless communications services and increase opposition to the development and expansion of tower sites. The potential connection between radio frequency emissions and certain negative health or environmental effects has been the subject of substantial study by the scientific community in recent years and numerous health-related lawsuits have limited experience operating asbeen filed against wireless carriers and wireless device manufacturers. If a REIT,scientific study or court decision resulted in a finding that radio frequency emissions pose health risks to consumers, it could negatively impact our tenants and the market for wireless services, which maycould materially and adversely affect our financial condition,business, results of operations cash flow and abilityor financial condition. We do not maintain any significant insurance with respect to satisfy debt service obligations.

We have only been operating as a REIT since January 1, 2012. Accordingly, the experience of our senior management operating a REIT is limited and may adversely affect our ability to qualify or remain qualified as a REIT. Failure to maintain REIT status could adversely affect our financial condition, results of operations, cash flow and ability to satisfy debt service obligations.these matters.

We could have liability under environmental and occupational safety and health laws.

Our operations like those of other companies engaged in similar businesses, are subject to the requirements of various federal, state, local and foreign environmental and occupational safety and health laws and regulations, including those relating to the management, use, storage, disposal, emission and remediation of, and exposure to, hazardous and non-hazardous substances, materials and wastes. As the owner, lessee or operator of real property and facilities, we may be liable for substantial costs of investigation, removal or remediation of soil and groundwater contaminated by hazardous materials, and for damages and costs relating to off-site migration of hazardous materials, without regard to whether we, as the owner, lessee or operator, knew of, or were responsible for, the contamination. We may also be liable for certain costs of remediating contamination at third-party sites to which we sent waste for disposal, even if the original disposal may have complied with all legal requirements at the time. Many of these laws and regulations contain information reporting and record keeping requirements. We cannot assure you that we are at all times in complete compliance with all environmental requirements. We may be subject to potentially significant fines or penalties if we fail to comply with any of these requirements. The requirements of these laws and regulations are complex, change frequently and could become more stringent in the future. In certain jurisdictions these laws and regulations could be applied or enforced retroactively. It is possible that these requirements will change or that liabilities will arise in the future in a manner that could have a material adverse effect on our business, results of operations or financial condition.

Our towers or data centers may be affected by natural disasters and other unforeseen events for which our insurance may not provide adequate coverage.

Our towers are subject to risks associated with natural disasters, such as ice and wind storms, tornadoes, floods, hurricanes and earthquakes, as well as other unforeseen events. Any damage or destruction to our towers or data centers, or certain unforeseen events, may impact our ability to provide services to our tenants. While we maintain insurance coverage for natural disasters, we may not have adequate insurance to cover the associated costs of repair or reconstruction for a major future event. Further, we carry business interruption insurance, but our insurance may not adequately cover all of our lost revenues, including potential revenues from new tenants that could have been added to our towers but for the event. If we are unable to provide services to our tenants, it could lead to tenant loss, resulting in a corresponding material adverse effect on our business, results of operations or financial condition.

Our costs could increase and our revenues could decrease due to perceived health risks from radio emissions, especially if these perceived risks are substantiated.

Public perception of possible health risks associated with cellular and other wireless communications technology could slow the growth of wireless companies, which could in turn slow our growth. In particular, negative public perception of, and regulations regarding, these perceived health risks could undermine the market acceptance of wireless communications services and increase opposition to the development and expansion of

tower sites. The potential connection between radio frequency emissions and certain negative health or environmental effects has been the subject of substantial study by the scientific community in recent years and numerous health-related lawsuits have been filed against wireless carriers and wireless device manufacturers. If a scientific study or court decision resulted in a finding that radio frequency emissions pose health risks to consumers, it could negatively impact our tenants and the market for wireless services, which could materially and adversely affect our business, results of operations or financial condition. We do not maintain any significant insurance with respect to these matters.

None.

Details of each of our principal offices as of December 31, 20122013 are provided below:

In addition to the principal offices set forth above, we maintain offices in the geographic areas we serve through which we operate our tower leasing and services businesses, as well as maintain offices to pursue international business development initiatives. We believe that our owned and leased facilities are suitable and adequate to meet our anticipated needs.

As of December 31, 2012,2013, we ownowned and operateoperated a portfolio of 54,60467,418 communications sites in the United States, Brazil, Chile, Colombia, Costa Rica, Germany, Ghana, India, Mexico, Panama, Peru, South Africa and Uganda. See the table in Item 7 of this Annual Report, under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Executive Overview” for more detailed information on the geographic locations of our communications sites. In addition, we own property interests that we lease to communications service providers and third-party tower operators in the United States, which are included in our domestic rental and management segment.

Domestic Rental and Management Segment. Our interests in our domestic communications sites are comprised of a variety of ownership interests, including leases created by long-term ground lease agreements, easements, licenses or rights-of-way granted by government entities. Pursuant to the loan agreement for our securitization transaction, the 5,278 tower sitesSecuritization, the 5,195 towers in the United States subject to our securitizationthe Securitization transaction as of December 31, 2012,2013, are subject to mortgages, deeds of trust and deeds to secure the loan. In addition, 1,4711,470 property interests in the United States are subject to mortgages and deeds of trust to secure notesthree separate classes of Secured Cellular Site Revenue Notes (the “Unison Notes”) assumed in connection with the acquisition of certain legal entities from Unison Holdings LLC and Unison Site Management II, L.L.C. (the “Unison Acquisition”). In connection with our acquisition of MIPT, we assumed approximately $1.49 billion principal amount of existing indebtedness under six series, consisting of eleven separate classes, of Secured Tower Revenue Notes issued by certain subsidiaries of GTP in several securitization transactions (the “GTP Notes”). The GTP Notes are secured by, among other things, 3,893 towers and 1,717 property interests and other related assets.

A typical domestic tower site consists of a compound enclosing the tower site, a tower structure and one or more equipment shelters that house a variety of transmitting, receiving and switching equipment. The principal types of our domestic towers are guyed, self-supporting lattice and monopole.

International Rental and Management Segment. Our interests in our international communications sites are comprised of a variety of ownership interests, including leases created by long-term ground lease agreements, easements, licenses or rights-of-way granted by private or government entities. Our financings in Colombia, Costa Rica and South Africa are secured by an aggregate of 2,148 towers.

A typical international tower site consists of a compound enclosing the tower site, a tower structure, backup or auxiliary power generators and batteries and one or more equipment shelters that house a variety of transmitting, receiving and switching equipment. The four principal types of our international towers are guyed, self-supporting lattice, monopole and rooftop. Guyed, self-supporting lattice and monopole structures are similar to those in our domestic segment. Rooftop towers are primarily used in metropolitan areas, where locations for traditional tower structures are unavailable. Rooftop towers typically have heights ranging from 10 to 100 feet.

Ground Leases.Of the 54,604 communications sites67,069 towers in our portfolio as of December 31, 2012,2013, approximately 88% arewere located on land we lease. Domestically, ground leases for land underlyingunder our towers generally have a term of

approximately twenty to twenty-five years, which is comprised of an initial term of approximately five years with three or four automatic five-year renewal periods. Internationally, ground leases, or similar agreements that grant use rights for land underlying our towers, typically also have a term of approximately twenty to twenty-five years, which is comprised of an initial term ranging from five to ten years with one or more automatic or exercisable renewal periods. As a result, approximately 78%74% of the ground agreements for our sites have a final expiration date of 20222023 and beyond.

Tenants. Our tenants are primarily wireless service providers, broadcasters and other communications service providers. As of December 31, 2012,2013, our four top tenants by total revenue were AT&T Mobility (18%), Sprint Nextel (14%(16%), Verizon Wireless (11%) and T-Mobile USA (8%(11%). In general, our tenant leases have an initial non-cancellable term of five to ten years, with multiple five-year renewal terms thereafter.terms. As a result, approximately 79%71% of our current tenant leases have a renewal date of 20182019 or beyond.

On June 2, 2011,We are involved in several lawsuits against TriStar Investors LLP and its affiliates (“TriStar”) in various states regarding single tower sites where TriStar has taken land interests under our owned or managed sites and we receivedbelieve TriStar has improperly induced the landowner to breach obligations to us. In addition, on February 16, 2012, TriStar brought a subpoena from the SEC requesting certain documents from 2007 through the date of the subpoena, including in particular documents related to our tax accounting and reporting. On November 6, 2012, the SEC notified us that its investigation has been completed. The SEC indicated that it does not intend to recommend any enforcementfederal action against us.

Oneus, in the United States District Court for the Northern District of Texas, in which TriStar principally alleges that we made misrepresentations to landowners when competing with TriStar for land under our subsidiaries, SpectraSite Communications, Inc. (“SCI”), a predecessor in interest by conversion to SpectraSite Communications, LLC, was involvedowned or managed sites. On January 22, 2013, we filed an amended answer and counterclaim against TriStar and certain of its employees, denying Tristar’s claims and asserting that TriStar has engaged in a lawsuit brought in Mexico against a former Mexican subsidiarypattern of SCI (the subsidiary of SCI was sold in 2002, priorunlawful activity, including: (i) entering into agreements not to our acquisition of SCI in 2005). The lawsuit concerns a terminated tower construction contractcompete for land under certain towers; and related agreements with a wireless carrier in Mexico. The primary issue for us is whether SCI itself can be found liable(ii) making widespread misrepresentations to landowners regarding both TriStar and us. TriStar and the Mexican carrier. The trial and lower appellate courts initially found that SCI had no such liability in part because Mexican courts did not have the necessary jurisdiction over SCI. In September 2010, following several decisions by Mexican appellate courts, including the Supreme Court of Mexico, and related appeals by both parties, an intermediate appellate court issued a new decisionCompany are each seeking injunctive relief that would have, if enforceable, re-imposed liability on SCI ifprohibit the primary defendant in the case were unable to satisfy the judgment. In its decision, the intermediate appellate court identified potential damages, in the form of potential statutory interest, of approximately $6.7 millionother party from making certain statements when interacting with landowners, as of that date. On October 14, 2010, we filed a new constitutional appeal to again dispute the decision, which was rejected on January 24, 2012. The case was returned to the trial court to determine whether any actual damages should be awarded to the Mexican carrier. On August 2, 2012, the trial court entered judgment against the primary defendant and SCI in the amount of approximately $6.5 million. Each party appealed the trial court’s determination and on October 17, 2012, the appellate court entered judgment against the primary defendant in the amount of approximately $7.9 million with SCI responsible for any amount not recoverable from the primary defendant. On November 9, 2012, SCI filed a constitutional appeal of the appellate court ruling. In connection with our acquisition of a portfolio of communications sites from the Mexican carrier on January 31, 2013, the Mexican carrier released all of its claims against SCI, including any obligation of SCI to pay anywell as damages.

We periodically become involved in various claims and lawsuits that are incidental to our business. In the opinion of management, after consultation with counsel, other than the legal proceeding discussed above and in note 19 to our consolidated financial statements included in this Annual Report, there are no matters currently pending that would, in the event of an adverse outcome, have a material impact on our consolidated financial position, results of operations or liquidity.

N/A.

PART II

The following table presents reported quarterly high and low per share sale prices of our common stock on the New York Stock Exchange (“NYSE”)NYSE for the years 20122013 and 2011.2012.

On February 11, 2013,14, 2014, the closing price of our common stock was $76.38$83.20 per share as reported on the NYSE. As of February  11, 2013,14, 2014, we had 395,103,065395,017,519 outstanding shares of common stock and 144176 registered holders.

Dividends

As a REIT, we must annually distribute to our stockholders an amount equal to at least 90% of our REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Generally, we expect to distribute all or substantially all of our REIT taxable income so as to not be subject to income tax or excise tax on undistributed REIT taxable income. The amount, timing and frequency of future distributions will be at the sole discretion of our Board of Directors and will be declared based upon various factors, a number of which may be beyond our control, including our financial condition and operating cash flows, the amount required to maintain REIT status and reduce any income and excise taxes that we otherwise would be required to pay, limitations on distributions in our existing and future debt instruments, our ability to utilize NOLsnet operating losses (“NOLs”) to offset our distribution requirements, limitations on our ability to fund distributions using cash generated through our TRSs and other factors that our Board of Directors may deem relevant.

During the year ended December 31, 2010, a pre-REIT year, there were no2013, we declared and paid the following regular cash distributions declared. Prior to our REIT Conversion, during the year ended December 31, 2011, we paid a one-time special cash distribution to our stockholders of approximately $137.8 million, or $0.35 per share of common stock. stockholders:

During the year ended December 31, 2012, we declared and paid the following regular cash distributions to our stockholders:

Performance Graph

This performance graph is furnished and shall not be deemed ‘‘filed’’ with the SEC or subject to Section 18 of the Exchange Act, nor shall it be deemed incorporated by reference in any of our filings under the Securities Act of 1933, as amended.

The following graph compares the cumulative total stockholder return on our common stock with the cumulative total return of the S&P 500 Index, and the Dow Jones U.S. Telecommunications Equipment Index and the FTSE NAREIT All Equity REITs Index. The performance graph assumes that on December 31, 2007,2008, $100 was invested in each of our common stock, the S&P 500 Index, and the Dow Jones U.S. Telecommunications Equipment Index and the FTSE NAREIT All Equity REITs Index. The cumulative return shown in the graph assumes reinvestment of all dividends. The performance of our common stock reflected below is not necessarily indicative of future performance.

Issuer Purchases of Equity Securities

During the three months ended December 31, 2012, we repurchased 619,314 shares of our common stock for an aggregate of approximately $46.0 million, including commissions and fees, pursuant to our publicly announced stock repurchase program, as follows:

We continued to repurchase shares of our common stock pursuant to our 2011 Buyback subsequent to December 31, 2012. Between January 1, 2013 and January 21, 2013, we repurchased an additional 15,790 shares of our common stock for an aggregate of $1.2 million, including commissions and fees, pursuant to the 2011 Buyback. As a result, as of January 21, 2013, we had repurchased a total of approximately 4.3 million shares of our common stock under the 2011 Buyback for an aggregate of $245.2 million, including commissions and fees. We expect to continue to manage the pacing of the remaining $1.3 billion under the 2011 Buyback in response to general market conditions and other relevant factors.

ITEM 6.

SELECTED FINANCIAL DATA

The selected financial data should be read in conjunction with our “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and our audited consolidated financial statements and the related notes to those consolidated financial statements included in this Annual Report.

In accordance with accounting principles generally accepted in the United States (“GAAP”), the consolidated statements of operations for all periods presented in this “Selected Financial Data” have been adjusted to reflect certain businesses as discontinued operations.

Year-over-year comparisons are significantly affected by our acquisitions, dispositions and to a lesser extent, construction of towers. Our acquisition of MIPT, which closed on October 1, 2013, significantly impacts the comparability of reported results between periods. Our principal acquisitions are described in note 6 to our consolidated financial statements included in this Annual Report.

ITEM 7.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The discussion and analysis of our financial condition and results of operations that follow are based upon our consolidated financial statements, which have been prepared in accordance with GAAP. The preparation of our financial statements requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, revenues and expenses and the related disclosure of contingent assets and liabilities at the date of our financial statements. Actual results may differ significantly from these estimates under different assumptions or conditions. This discussion should be read in conjunction with our consolidated financial statements herein and the accompanying notes thereto, and the information set forth under the caption “Critical Accounting Policies and Estimates” below.

Our continuing operations are reported in three segments, domestic rental and management, international rental and management and network and development services. Among other factors, management uses segment gross margin and segment operating profit in its assessment of operating performance in each business segment. We define segment gross margin as segment revenue less segment operating expenses, excluding stock-based compensation expense recorded in costs of operations; depreciation,Depreciation, amortization and accretion; selling,Selling, general, administrative and development expense; and otherOther operating expense. We define segment operating profit as segment gross margin less selling,Selling, general, administrative and development expense attributable to the segment, excluding stock-based compensation expense and corporate expenses. Segment gross margin and segment operating profit for the international rental and management segment also include interestInterest income, TV Azteca, net (see note 2021 to our consolidated financial statements included herein). These measures of segment gross margin and segment operating profit are also before interestInterest income, interestInterest expense, lossLoss on retirement of long-term obligations, otherOther income (expense), netNet income (loss) attributable to noncontrolling interest, incomeIncome (loss) on equity method investments income taxes and discontinued operations.Income tax provision (benefit).

Executive Overview

Our primary business is leasing antenna space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. In addition to the communications sites in our portfolio, we manage rooftop and tower sites for property owners under various contractual arrangements. We also hold property interests that we lease to communications service providers and third-party tower operators. We refer to this business as our rental and management operations, which accounted for approximately 97%98% of our total revenues for the year ended December 31, 20122013 and includes our domestic rental and management segment and our international rental and management segment. Through our network development services, segment, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites. We began operating as a REIT for federal income tax purposes effective January 1, 2012.

The following table details the number of communications sites we ownowned or operate in the countries in which we operateoperated as of December 31, 2012:2013:

The majority of our tenant leases with wireless carriers are typically forhave an initial non-cancellable term of five to ten years, with multiple five-year renewal terms thereafter.terms. Accordingly, nearly all of the revenue generated by our rental and management operations during the year ended December 31, 2012 is2013 was recurring revenue that we should continue to receive in future periods. Based upon foreign currency exchange rates and the tenant leases in place as of December 31, 2012,2013, we expect to generate approximately $20$23 billion of non-cancellable tenant lease revenue over future periods, excludingabsent the impact of straight-line lease accounting. In addition, mostMost of our tenant leases have provisions that periodically increase the rent due under the lease, typically annually based on a fixed percentage (on average approximately 3.5%escalation (approximately 3.0%-3.5% in the United States), inflation, or inflation with a fixed minimum or maximum escalation for the year. Revenue generated by rent increases based on fixed escalation clauses is recognized on a straight line basis over the non-cancellable term of the applicable agreement. We also routinely seek to extend our leases with our tenants, which increases the non-cancellable term of the lease and creates incremental growthan inflationary index in our revenues.international markets.

The revenues generated by our rental and management operations may also be affected by cancellations of existing tenant leases. As discussed above, most of our tenant leases with wireless carriers and broadcasters are multi-year contracts, which typically are non-cancellable; however in some instances, a lease may be cancelledcanceled upon the payment of a termination fee.

Revenue lost from either cancellations of leases at the end of their terms or rent negotiations historically have not had a material adverse effect on the revenues generated by our rental and management operations. During the year ended December 31, 2012,2013, loss of annual revenue from tenant lease cancellations or renegotiations represented less than 1.3%1.5% of our rental and management operations revenues.

Rental and Management Operations Revenue Growth. Our rental and management revenue growth is comprised of (i) growth in organic revenue, which is revenue from sites that existed in our portfolio as of the beginning of the prior year period (“legacy sites”) and (ii) growth from sites acquired or constructed since the beginning of the prior year period (“new sites”). The primary factors affecting the revenue growth forof our domestic and international rental and management segments are:

We continue to believe that our site leasing revenue is likely to increase due to the growing use of wireless communications services and our ability to meet thatthe corresponding incremental demand for wireless real estate by adding new tenants and new equipment for existing tenants on our legacy sites, which increases thethese sites’ utilization and profitability of our sites.profitability. In addition, we believe the majority of our site leasing activity will continue to come from wireless service providers. Our legacy site portfolio and our established tenant base provide us with new business opportunities, which have historically resulted in consistent and predictable organic revenue growth as wireless carriers seek to increase the coverage and capacity of their existing networks, as well as roll outwhile also deploying next generation wireless technologies. In addition, consistent with our strategic acquisition of MIPT, we intend to continue to supplement the organic growth on our legacy sites by selectively developing or acquiring new sites in our existing and new markets where we can achieve our risk adjusted return on investment criteria.

Rental and Management Operations Organic Revenue Growth. Consistent with our strategy to increase the utilization and return on investment of our legacy sites, our objective is to add new tenants and new equipment for existing tenants through collocation.collocation and lease amendments. Our ability to lease additional space on our sites is primarily a function of the rate at which wireless carriers deploy capital to improve and expand their wireless networks. This rate, in turn, is influenced by the growth of wireless communications services, and related infrastructure needs,the penetration of advanced wireless devices, the financial performance of our tenants and their access to capital, and general economic conditions. The following key trends within each market that we serve provide opportunities for organic revenue growth:

We expect the following key industry trends will result in incremental revenue opportunities for us:

We signedhave entered into holistic master lease agreements with three of our four majorlargest tenants in the United States, which provide for consistent, long-term revenue growth and a reduction in the potential impactlikelihood of churn. Typically, these agreements include built-in annual escalators, fixed annual charges which permit our tenants to place a pre-determined amount of equipment on certain of our sites and provisions for incremental lease payments if the equipment levels are exceeded. Our holistic master lease agreements build and fosteraugment strong strategic partnerships with our tenants and have significantly reduced collocation cycle times, thereby providing our tenants with the ability to rapidly and efficiently deploy technologyequipment on our sites.

continue to be deployed as wireless service providers are beginning their investments in 3G data networks. Similarly, in Ghana and Uganda, wireless service providers continue to build out their voice and data networksdevelopment in order to satisfy increasing demand fordiversify our international exposure and position us to benefit from a number of different wireless services.technology deployments over the long term. In South Africa, where voice networks are in a more advanced stageaddition, we have focused on building relationships with large multinational carriers such as MTN, Telefónica and Vodafone as part of development, carriers are beginning to deploy 3G data networks across spectrum acquired in recent spectrum auctions. In Mexico and Brazil, where nationwide voice networks have also been deployed, some incumbent wireless service providers continue to investour expansion efforts. We believe that consistent carrier investments in their 3G data networks and recent spectrum auctions have enabled other incumbent wireless service providers to begin their initial investments in 3G data networks. In markets such as Chile, Peru and Colombia, recent or anticipated spectrum auctions are expected to drive investment in nationwide voice and 3G data networks. In Germany, our most mature international wireless market, demand is currently being driven by a government-mandated rural fourth generation network build-out, as well as other tenant initiatives to deploy next generation wireless services. We believe incremental demand for our tower sites will continue inacross our international markets as wireless service providers seekposition us to remain competitive by increasing the coverage of their networks while also investing in next generation data networks.generate meaningful organic revenue growth going forward.

In emerging markets such as India, Ghana and Uganda, wireless networks tend to be significantly less advanced than those in the United States, and initial voice networks continue to be deployed in underdeveloped areas. In more developed urban locations within these markets, early-stage data network deployments are also underway. Carriers are focused on completing voice network build-outs while also investing in initial data networks as wireless data usage and smartphone penetration within their customer bases begin to accelerate.

In markets with rapidly evolving network technology, such as South Africa and most of the countries in Latin America where we do business, initial voice networks, for the most part, have already been built out, and carriers are focused on third generation (3G) network build outs, with select investments in fourth generation (4G) technology. Recent spectrum auctions in these rapidly evolving markets have allowed incumbent carriers to accelerate their data network deployments and have also enabled new entrants to begin initial investments in data networks. Smartphone penetration and wireless data usage in these markets are growing rapidly, which mandates that carriers continue to invest in their networks in order to maintain and augment their quality of service.

Finally, in markets with more mature network technology such as Germany and Panama, carriers are focused on deploying 4G data networks to account for rapidly increasing wireless data usage. With a more mature customer base, higher smartphone penetration and significantly higher per capita data usage, carrier investment in networks is focused on 4G coverage and capacity.

We believe that the network technology migration we have seen in the United States, which has led to significantly denser networks and meaningful new business commencements for us over a number of years, will ultimately be replicated in our less advanced international markets. As a result, we expect to be able to leverage our extensive international portfolio of approximately 39,400 communications sites and the relationships we have built with our carrier customers to drive sustainable, long-term growth.

Rental and Management Operations New Site Revenue Growth.The results of operations of MIPT have been included in our consolidated results of operations since October 1, 2013, the date of the acquisition. During the period from October 1, 2013 to December 31, 2013, MIPT generated total revenues of $84.1 million and gross margin of $65.0 million. In addition to the approximately 5,370 sites acquired through the acquisition of MIPT, during the year ended December 31, 2012,2013, we grew our portfolio of communications real estate through acquisitions and construction activities, including the acquisition and construction of approximately 8,8107,700 sites. In a majority of our international markets, the acquisition or construction of new sites results in increased pass-through revenues (such as ground rent or fuel costs) and expenses. We continue to evaluate opportunities to acquire larger communications real estate portfolios, both domestically and internationally, to determine whether they meet our risk adjusted hurdle rates and whether we believe we can effectively integrate them into our existing portfolio.

Network Development Services Segment Revenue Growth. As we continue to focus on growing our rental and management operations, we anticipate that our network development services revenue will continue to represent a relatively small percentage of our total revenues. Through our network development services segment, we offer tower-related services, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites, including in connection with provider network upgrades.

Rental and Management Operations Expenses.Direct operating expenses incurred by our domestic and international rental and management segments include direct site level expenses and consist primarily of ground rent, property taxes, repairs and maintenance, security and power and fuel costs, some of which may be passed through to our tenants. These segment direct operating expenses exclude all segment and corporate selling, general, administrative and development expenses, which are aggregated into one line item entitled selling,Selling, general, administrative and development expense in our consolidated statements of operations. In general, our domestic and international rental and management segmentssegments’ selling, general, administrative and development expenses do not significantly increase as a result of adding incremental tenants to our legacy sites and typically increase only modestly year-over-year. As a result, leasing additional space to new tenants on our legacy sites provides significant incremental cash flow. We may incur additional segment selling, general, administrative and development expenses as we increase our presence in geographic areas where we have recently launched operations or are focused on expanding our portfolio. Our profit margin growth is therefore positively impacted by the addition of new tenants to our legacy sites and can be temporarily diluted by our development activities.

REIT Conversion. We began operating as a REIT effective January 1, 2012. The REIT tax rules require that we derive most of our income, other than income generated by a TRS, from investments in real estate, which for us primarily consists of income from the leasing of our communications sites. Under the Code, maintaining REIT status generally requires that no more than 25% of the value of the REIT’s assets be represented by securities of one or more TRSs and other non-qualifying assets.

A REIT must annually distribute to its stockholders an amount equal to at least 90% of its REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). During the year ended December 31, 2012, we paid an aggregate of approximately $355.6 million in regular cash distributions to our stockholders. We intend to continue paying regular distributions in 2013. The amount, timing and frequency of future distributions will be at the sole discretion of our Board of Directors and will be declared based upon various factors, a number of which may be beyond our control, including our financial condition and operating cash flows, the amount required to maintain REIT status and reduce any income and excise taxes that we otherwise would be required to pay, limitations on distributions in our existing and future debt instruments, our ability to utilize NOLs to offset, in whole or in part, our distribution requirements, limitations on our ability to fund distributions using cash generated through our TRSs and other factors that our Board of Directors may deem relevant.

For more information on the requirements to qualify as a REIT, see Item 1 of this Annual Report under the caption “Business—Overview,” and Item 1A of this Annual Report under the caption “Risk Factors—If we fail to qualify as a REIT or fail to remain qualified as a REIT, we would be subject to tax at corporate income tax rates, which would substantially reduce funds otherwise available” and “—Certain of our business activities may be subject to corporate level income tax and foreign taxes, which reduce our cash flows, and may have deferred and contingent tax liabilities.”

Non-GAAP Financial Measures

Included in our analysis of our results of operations are discussions regarding earnings before interest, taxes, depreciation, amortization and accretion, as adjusted (“Adjusted EBITDA”), Funds From Operations, as defined by the National Association of Real Estate Investment Trusts (“NAREIT FFO”), and Adjusted Funds From Operations (“AFFO”).

We define Adjusted EBITDA as netNet income before: incomebefore Income (loss) on discontinued operations, net; incomeIncome (loss) fromon equity method investments; incomeIncome tax provision (benefit); otherOther income (expense); lossLoss on retirement of long-term obligations; interestInterest expense; interestInterest income; otherOther operating expenses; depreciation,income (expense); Depreciation, amortization and accretion; and stock-based compensation expense.

NAREIT FFO is defined as net income before gains or losses from the sale or disposal of real estate, real estate related impairment charges and real estate related depreciation, amortization and accretion, and including adjustments for (i) unconsolidated affiliates and (ii) noncontrolling interest.

We define AFFO as NAREIT FFO before (i) straight-line revenue and expense; (ii) stock-based compensation expense; (iii) the non-cash portion of our tax provision; (iv) non-real estate related depreciation, amortization and accretion; (v) amortization of deferred financing costs, capitalized interest, debt discounts and premiums and long-term deferred interest charges; (vi) other income (expense); (vii) loss on retirement of long-term obligations; (viii) other operating income (expense); and adjustments for (ix) unconsolidated affiliates and (x) noncontrolling interest, less cash payments related to capital improvements and cash payments related to corporate capital expenditures.

Adjusted EBITDA, isNAREIT FFO and AFFO are not intended to replace net income or any other performance measures determined in accordance with GAAP. Neither NAREIT FFO nor AFFO represent cash flows from operating activities in accordance with GAAP and, therefore, these measures should not be considered indicative of cash flows from operating activities as a measure of liquidity or of funds available to fund our cash needs, including our ability to make cash distributions. Rather, Adjusted EBITDA, isNAREIT FFO and AFFO are presented as we believe iteach is a useful indicator of our current operating performance. We believe that Adjusted EBITDA isthese metrics are useful to an investor in evaluating our operating performance because (1) iteach is a

key measure used by our management team for purposes of decision making and for evaluating the performance of our operating segments; (2) itAdjusted EBITDA is a component of the calculation used by our lenders to determine compliance with certain debt covenants; (3) itAdjusted EBITDA is widely used in the tower industry to measure operating performance as depreciation, amortization and accretion may vary significantly among companies depending upon accounting methods and useful lives, particularly where acquisitions and non-operating factors are involved; (4) iteach provides investors with a meaningful measure for evaluating our period to periodperiod-to-period operating performance by eliminating items whichthat are not operational in nature; and (5) iteach provides investors with a measure for comparing our results of operations to those of different companies by excluding the impact of long-term strategic decisions which can differ significantly from company to company, such as decisions with respect to capital structure, capital investments and the tax jurisdictions in which companies operate.other companies.

Our measurement of Adjusted EBITDA, NAREIT FFO and AFFO may not, however, be fully comparable to similarly titled measures used by other companies. A reconciliationReconciliations of Adjusted EBITDA, NAREIT FFO and AFFO to net income, the most directly comparable GAAP measure, hashave been included below.

Results of Operations

Years Ended December 31, 2013 and 2012

(in thousands, except percentages)

Revenue

Total revenues for the year ended December 31, 2013 increased 17% to $3,361.4 million. The increase was primarily attributable to an increase in both of our rental and management segments, including organic revenue growth attributable to our legacy sites and revenue growth attributable to the approximately 21,880 new sites that we have constructed or acquired since January 1, 2012. Approximately $84.1 million of the increase was attributable to revenues generated by MIPT.

Domestic rental and management segment revenue for the year ended December 31, 2013 increased 13% to $2,189.4 million. This growth was comprised of:

International rental and management segment revenue for the year ended December 31, 2013 increased 27% to $1,097.7 million. This growth was comprised of:

Network development services segment revenue for the year ended December 31, 2013 increased 3% to $74.3 million. The growth was primarily attributable to an increase in structural engineering services and site acquisition, zoning and permitting services as a result of an increase in tenant lease applications, which are primarily associated with certain tenants’ next generation technology network upgrade projects during the year ended December 31, 2013.

Gross Margin