USG Corporation (NYSE: USG), a leading building products company, announced today that its Board of Directors amended the Corporation’s existing stockholder rights plan to lower the ownership threshold to a level that could provide protection to USG’s net operating loss carryforwards (“NOLs”) and related deferred tax assets. The amendment reduces the ownership threshold under USG's shareholder rights plan from 15 percent to 4.9 percent until March 22, 2016 (or earlier, if the Board determines that the amendment is no longer necessary to protect the NOLs). USG has over $2 billion in NOLs, a portion of which would be at risk if an “ownership change” under Internal Revenue Code Section 382 were to occur. An “ownership change” occurs if, during a rolling three-year period, the cumulative percentage of stock owned by one or more 5-percent shareholders, which would include those who have acquired their shares in the public market, has increased by more than 50 percentage points. “After careful consideration, we have determined that it is in the best interests of the company and our stockholders to modify the beneficial ownership threshold under our rights plan,” said USG Corporation Chairman, President and CEO James S. Metcalf. “The NOLs are a valuable asset of USG. We are taking these steps in an effort to maximize our ability to offset income that we expect to generate in the future.” The rights plan, as amended, is designed to deter any person or group from acquiring beneficial ownership of more than 4.9 percent of USG's common stock. The rights plan amendment exempts stockholders whose current beneficial ownership exceeds 4.9 percent so long as they do not acquire any additional shares of common stock, subject to specified exceptions. Additional information regarding the amendment is contained in a Current Report on Form 8-K and in an amendment to a Registration Statement on Form 8-A that USG filed today with the Securities and Exchange Commission. These filings are available on the SEC's Web site at www.sec.gov. About USG USG Corporation is a manufacturer and distributor of high-performance building systems through its United States Gypsum Company, USG Interiors, LLC, L&W Supply Corporation and other subsidiaries. Headquartered in Chicago, USG’s worldwide operations serve the commercial, residential, and repair and remodel construction markets. USG’s wall, ceiling, flooring and roofing products provide leading-edge building solutions for customers, while L&W Supply branch locations efficiently stock and deliver building materials nationwide. For additional information, visit the USG website at www.usg.com.