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. Yesþ Noo

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). Yesoþ Noo

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

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).Yeso Noþ

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

The condensed consolidated financial statements included herein have been prepared by A. M. Castle & Co. and subsidiaries (the “Company”), without audit, pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). The Condensed Consolidated Balance Sheet at December 31, 2010 is derived from the audited financial statements at that date. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the SEC. In the opinion of management, the unaudited statements, included herein, contain all adjustments (consisting of only normal recurring adjustments) necessary for a fair presentation of financial results for the interim period.periods. It is suggested that these condensed consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s latest Annual Report on Form 10-K. The 2011 interim results reported herein may not necessarily be indicative of the results of the Company’s operations for the full year.

Non-cash investing activities for the threesix months ended March 31,June 30, 2011 and 2010 consisted of $220$348 and $169$84 of capital expenditures financed by accounts payable, respectively.

Effective January 1, 2011, the Company adopted Accounting Standards Update (“ASU”) No. 2010-29, “Disclosure of Supplementary Pro Forma Information for Business Combinations.” The ASU specifies that if a public entity presents comparative financial statements, the entity should disclose revenue and earnings of the combined entity as though the business combination that occurred during the current year had occurred as of the beginning of the comparable prior annual reporting period only. The amendments to this guidance also expand the supplemental pro forma disclosures to include a description of the nature and amount of material, nonrecurring pro forma adjustments directly attributable to the business combination included in the reported pro forma revenue and earnings. The adoption of the ASU will impact disclosures in future interim and annual financial statements issued if the Company enters into business combinations.

Diluted earnings per share is computed by dividing net income by the weighted average number of shares of common stock plus common stock equivalents. Common stock equivalents consist of employee and director stock options, restricted stock awards, and other share-based payment awards, which have been included in the calculation of weighted average shares outstanding using the treasury stock method. The following table is a reconciliation of the basic and diluted earnings per share calculations for the three and six months ended March 31,June 30, 2011 and 2010:

Long-termShort-term and long-term debt consisted of the following:

The U.S. Revolver A and the Canadian revolver are classified as short-term based on the Company’s ability and intent to repay amounts outstanding under these instruments within the U.S. Revolver A.next 12 months. The U.S. Revolver B is classified as long-term as the Company’s cash projections indicate that amounts outstanding (which are denominated in British pounds) under this instrument are not expected to be repaid within the next 12 months. Available revolving credit capacity is primarily used to fund working capital needs. Taking into consideration the most recent borrowing base calculation as of March 31,June 30, 2011, which reflects trade receivables, inventory, letters of credit and other outstanding secured indebtedness, available credit capacity consisted of the following:

The Company distributes and performs processing on both metals and plastics. Although the distribution processes are similar, the customer markets, supplier bases and types of products are different. Additionally, the Company’s Chief Executive Officer, the chief operating decision-maker, reviews and manages these two businesses separately. As such, these businesses are considered reportable segments and are reported accordingly.

In its Metals segment, the Company’s marketing strategy focuses on distributing highly engineered specialty grades and alloys of metals as well as providing specialized processing services designed to meet very precise specifications. Core products include alloy, aluminum, stainless, nickel, titanium and carbon. Inventories of these products assume many forms such as plate, sheet, extrusions, round bar, hexagon bar, square and flat bar, tubing and coil. Depending on the size of the facility and the nature of the markets it serves, service centers are equipped as needed with bar saws, plate saws, oxygen and plasma arc flame cutting machinery, water-jet cutting, stress relieving and annealing furnaces, surface grinding equipment and sheet shearing equipment. This segment also performs various specialized fabrications for its customers through pre-qualified subcontractors that thermally process, turn, polish and straighten alloy and carbon bar.

The Company’s Plastics segment consists exclusively of a wholly-owned subsidiary that operates as Total Plastics, Inc. (“TPI”) headquartered in Kalamazoo, Michigan, and its wholly-ownedwholly owned subsidiaries. The Plastics segment stocks and distributes a wide variety of plastics in forms that include plate, rod, tube, clear sheet, tape, gaskets and fittings. Processing activities within this segment include cut to length, cut to shape, bending and forming according to customer specifications. The Plastics segment’s diverse customer base consists of companies in the retail (point-of-purchase), marine, office furniture and fixtures, safety products, life sciences applications, transportation and general manufacturing industries. TPI has locations throughout the upper northeast and midwest regions of the U.S. and one facility in Florida from which it services a wide variety of users of industrial plastics.

The accounting policies of all segments are the same as described inNote 1, “Basis of Presentation and Significant Accounting Policies” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2010. Management evaluates the performance of its business segments based on operating income.

“Other” — Operating income (loss)loss includes the costs of executive, legal and finance departments, which are shared by both the Metals and Plastics segments.

Below are reconciliations of segment data to the consolidated financial statements:statements for the three months ended June 30, 2011 and 2010:

Segment information for total assets is as follows:

The following is a summary of the estimated annual amortization expense for 2011 and each of the next 4 years:

PSUs containing a market-based performance condition- the potential award for PSUs containing a market-based performance condition is dependent on relative total shareholder return (“RTSR”), which is measured over a three-year performance period, beginning January 1^st of the year of grant. RTSR is measured against a group of peer companies either in the metals industry or in the industrial products distribution industry (the “RTSR Peer Group”). The number of performance shares, if any, that vest based on the performance achieved during the three-year performance period, will vest at the end of the three-year performance period. Compensation expense for performance awards containing a market condition is recognized regardless of whether the market condition is achieved to the extent the requisite service period condition is met. Each performance share that becomes vested entitles the participant to receive one share of the Company’s common stock. The number of shares delivered may be reduced by the number of shares required to be withheld for federal and state withholding tax requirements (determined at the market price of Company shares at the time of payout).

Comprehensive income (loss) includes net income (loss) and all other non-owner changes to equity that are not reported in net income (loss). The Company’s comprehensive income (loss) for the three months ended March 31,June 30, 2011 and 2010 is as follows:

As of March 31,June 30, 2011, the Company had not made any cash contributions to its pension plans for this fiscal year and does not anticipate making any significant cash contributions to its pension plans in 2011.

Kreher Steel Co., LLC is a 50% owned joint venture of the Company. It is a metals distributor of bulk quantities of alloy, special bar quality and stainless steel bars, headquartered in Melrose Park, Illinois.

The following information summarizes financial data for this joint venture for the three months ended March 31,June 30, 2011 and 2010:

The Company is a defendant in several lawsuits arising from the operation of its business. These lawsuits are incidental and occur in the normal course of the Company’s business affairs. It is the opinion of management, based on current knowledge, that no uninsured liability will result from the outcome of this litigation that would have a material adverse effect on the consolidated results of operations, financial condition or cash flows of the Company.

In April 2011, the United States Department of Commerce, U.S. Bureau of Industry and Security (BIS)(“BIS”), provided the Company with a proposed charging letter claiming it had violated export control regulations in connection with certain shipments of aluminum alloy bar between 2005 and January 2008 to customers in four countries (China, Malaysia, Mexico and Singapore), without the required export licenses. The Company had previously submitted to the BIS a voluntary self disclosure relating to these shipments, and export licenses were subsequently obtained for all shipments. The relevant export statutes provide for monetary penalties, and in some instances, denial of export privileges and exclusion from practice before the BIS if a violation is found. The Company is in on-going discussions with the BIS authorities regarding this matter. Absent a negotiated resolution, an administrative hearing would be set and, in such case, the Company would assert a vigorous defense. WhileSecond quarter 2011 results include a $750 charge for the ultimate disposition ofpotential penalties associated with this matter cannot be predicted with certainty, it is the opinion of management, based on the information available at this time, that the outcome of this matter will not have a material adverse effect on the Company’s financial position, results of operations or cash flows.claim.

The Company or its subsidiaries files income tax returns in the U.S., 29 states and 7 foreign jurisdictions. The tax years 2007 through 2010 remain open to examination by the major taxing jurisdictions to which the Company or its subsidiaries is subject.

An audit of the Company’s 2008 and 2009 U.S. federal income tax returns is scheduled forcommenced during the second quarter of 2011. To date, no material issues have been raised. Due to the potential for resolution of the examination or expiration of statues of limitations, it is reasonably possible that the Company’s gross unrecognized tax benefits may change within the next 12 months by a range of zero to $1,361.$1,350.

The Company received its 2009 federal income tax refund of $6,344 during January 2011.

A. M. Castle & Co. and subsidiaries (the “Company”) experienced higher demand from its customer base in the firstsecond quarter of 2011 in both the Metals and Plastics segments, reflecting the continuing recovery in the global industrial economy and strength in many of the Company’s targeted end markets.

Metals segment sales increased 22.5%18.3% from the firstsecond quarter of 2010. Average tons sold per day increased 17.7%18.1%, compared to the prior year quarter, which was primarily driven by growth in alloy bar, carbon bar and SBQ bar products.volume increases. Key end-use markets that experienced increased demand in the firstsecond quarter include oil and gas, mining and heavy equipment and general industrial and heavy equipment.markets.

Management uses the PMI provided by the Institute for Supply Management (website is www.ism.ws) as an external indicator for tracking the demand outlook and possible trends in its general manufacturing markets. The table below shows PMI trends from the first quarter of 2009 through the firstsecond quarter of 2011. Generally speaking, an index above 50.0 indicates growth in the manufacturing sector of the U.S. economy, while readings under 50.0 indicate contraction.

Consolidated net sales were $272.8$282.6 million, an increase of $49.8$42.5 million, or 22.3%17.7%, compared to the firstsecond quarter of 2010. Higher net sales in the firstsecond quarter of 2011 were primarily the result of higher shipping volumes and increased pricing in the metals and plastics markets. Metals segment sales during the firstsecond quarter of 2011 of $244.6$252.3 million were $44.9$39.0 million, or 22.5%18.3%, higher than the same period last year. Average tons sold per day increased 17.7%18.1% compared to the prior year quarter. The first quarter of 2011 had one more shipping day than the prior year quarter. The increase in sales volume was driven primarily by alloy bar carbon bar and SBQ bar products. Key end-use markets that experienced increased demand in the firstsecond quarter include oil and gas, mining and heavy equipment and general industrial and heavy equipment.markets.

Plastics segment sales during the firstsecond quarter of 2011 of $28.2$30.3 million were $4.9$3.5 million, or 21.0%13.1% higher than the firstsecond quarter of 2010 due to increased pricing and higher sales volume reflecting continued strength in virtually all end-use markets, most notably in the automotive, life sciences and retail point-of-purchase display sectors.

Cost of materials (exclusive of depreciation and amortization) during the firstsecond quarter of 2011 was $201.4$208.5 million, an increase of $32.4$30.0 million, or 19.2%16.8%, compared to the firstsecond quarter of 2010. Material costs for the Metals segment for the firstsecond quarter of 2011 were $182.0was $187.5 million or 74.4%74.3% as a percent of net sales compared to $153.0$160.4 million or 76.6%75.2% as a percent of net sales for the firstsecond quarter of 2010. Material costs as a percentage of net sales were lower in the firstsecond quarter of 2011 than 2010 as the demand environment continued to improve in firstthe second quarter of 2011, which provided an improved pricing environment compared to the firstsecond quarter of 2010. As market prices for many products increased throughout the quarter, the Company was able to leverage its inventory position, which also contributed to the reduction in material costs as a percentage of net sales compared to the prior year period. The Metals segment recorded LIFO expense of $3.9 million in second quarter of 2011 and $3.0 million in the first quarter of 2011 and $2.0 million in the firstsecond quarter of 2010. Material costs for the Plastics segment of 68.8%were 69.3% as a percent of net sales for the firstsecond quarter of 2011 were consistent with 68.7%as compared to 67.5% for the same period last year. Management believes that consolidated material costs as a percentage of net sales will be comparable to firstsecond quarter 2011 levels for the balance of 2011.

On a consolidated basis, operating costs and expenses increased $8.3$8.5 million, or 13.6%13.9%, compared to the firstsecond quarter of 2010. Operating costs and expenses were $69.3$69.8 million, or 25.4%24.7% of net sales, compared to $61.0$61.3 million, or 27.4%25.5% of net sales during the firstsecond quarter of 2010. Second quarter 2011 results include a $0.8 million charge for potential export penalties related to product shipments that occurred from 2005 to 2008. The increase in operating expenses for the firstsecond quarter of 2011 compared to the firstsecond quarter of 2010 primarily relates to the following:

The Company recorded income tax expense of $1.3$2.5 million for the quarter ended March 31,2011June 30, 2011 compared to an income tax benefitexpense of $2.9$0.1 million for the same period last year. The Company’s effective tax rate is expressed as ‘Income tax expense or benefit’ as a percentage of ‘Income (loss) before income taxes and equity in earnings of joint venture.’ This calculation includes taxes on the joint venture income but excludes joint venture income. The effective tax rate for the quarters ended March 31,June 30, 2011 and 2010 were 114.0%77.5% and 34.2%7.2%, respectively. The increase in the effective tax rate for the second quarter of 2011 compared to the firstsecond quarter of 2010 was primarily the result of higher earnings of the Company’s joint venture.venture, as the joint venture earnings are not reflected in reported pre-tax income.

Equity in earnings of the Company’s joint venture was $2.9$3.0 million in the firstsecond quarter of 2011, compared to $0.9$1.4 million for the same period last year. The increase is a result of higher demand in virtually all end-use markets, most notably the automotive and energy sectors, and higher pricing for Kreher’s products compared to the same period last year.