COPT Prices $350M of Senior Unsecured Notes

Corporate Office Properties Trust

announced that its operating partnership, Corporate Office Properties, L.P. (the "Operating Partnership"), has priced an offering of $350 million aggregate principal amount of 3.60% senior unsecured notes due May 15, 2023 (the "Notes") at a price equal to 99.816% of the principal amount. The Notes will be senior unsecured obligations of the operating partnership and will be fully and unconditionally guaranteed by COPT. The Operating Partnership intends to use the net proceeds from the offering of the Notes to repay borrowings under its senior unsecured revolving credit facility and for general corporate purposes, including potential repayment of certain unsecured term loans. The sale of the Notes is expected to close on May 6, 2013, subject to customary conditions. The Notes and related guarantee are being offered and sold in the United States only to qualified institutional buyers under Rule 144A under the Securities Act of 1933, as amended (the "Securities Act") and to non-U.S. persons outside the United States under Regulation S under the Securities Act. The Notes and related guarantee have not been registered under the Securities Act or the securities laws of any other place and, unless so registered, may not be offered or sold in the United States except pursuant to an exemption from, or in a transaction not subject to, the registration requirements of the Securities Act and applicable state securities laws. This announcement shall not constitute an offer to sell or the solicitation of an offer to buy the Notes or related guarantee nor shall there be any sale of the notes in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. This notice is being issued pursuant to and in accordance with Rule 135c of the Securities Act. Company Information COPT is an office REIT that focuses primarily on serving the specialized requirements of U.S. Government agencies and defense contractors, most of whom are engaged in defense information technology and national security-related activities. The Company generally acquires, develops, manages and leases office and data center properties concentrated in large office parks primarily located near knowledge-based government demand drivers and/or in targeted markets or submarkets in the Greater Washington, DC/Baltimore region. As of March 31, 2013, the Company's consolidated portfolio consisted of 210 office properties totaling 19.1 million rentable square feet. COPT is an S&P MidCap 400 company.