Exhibit 10.1

TWENTY-THIRD AMENDMENT
TO
SECOND AMENDED AND RESTATED
LIMITED PARTNERSHIP AGREEMENT
OF
CORPORATE OFFICE PROPERTIES, L.P.

This Twenty-Third Amendment (the Amendment) to the Second Amended and Restated Limited Partnership Agreement Of Corporate Office Properties, L.P., a Delaware limited partnership (the Partnership), is made and entered into as of April 6, 2007, by the undersigned.

Recitals

A.            The Partnership is a limited partnership organized under the Delaware Revised Uniform Limited Partnership Act and governed by that certain Second Amended and Restated Limited Partnership Agreement dated as of December 7, 1999, as amended to the date hereof (as amended, the “Partnership Agreement”).

B.            The sole general partner of the Partnership is Corporate Office Properties Trust, a real estate investment trust formed under the laws of the State of Maryland (the “General Partner”).

C.            Pursuant to Section 11.1 (b) (iii), the General Partner desires to amend the Partnership Agreement to reflect the admission, substitution, termination and/or withdrawal of various limited partners in accordance with the terms of the Partnership Agreement.

NOW THEREFORE, the General Partner, intending to be legally bound, hereby amends the Partnership Agreement as follows, effective as of the date first set forth above.

1.                                       Exhibit 1, Schedule of Partners, as attached hereto and by this reference made a part hereof, is hereby substituted for and intended to replace any prior Exhibit 1 attached to a prior Amendment to the Partnership Agreement, and as attached hereto shall be a full and complete listing of all the general and limited partners of the Partnership as of the date of this Amendment, same being intended and hereby superceding all prior Exhibit 1 listings.

In Witness Whereof, the General Partner has executed this Amendment as of the day and year first above written.

	Corporate Office Properties Trust, a
	Maryland Real Estate Investment Trust
	By:	/s/ RANDALL M. GRIFFIN
		Randall M. Griffin
		President and Chief Executive Officer

 

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Exhibit 1 Addendum

Schedule of Partners

General Partner				Common Units of  Partnership  Units		Series G Preferred  Units		Series H Preferred Units		Series I Preferred Units		Series J Preferred Units		Series K Preferred Units
Corporate Office Properties Trust				44,938,069		2,200,000		2,000,000				3,390,000		531,667
Limited Partners and Preferred Limited Partners
Jay H. Shidler				452,878
Shidler Equities, L.P.				2,995,439
Clay W. Hamlin, III				489,917
LBCW Limited Partnership				2,681,107
Robert L. Denton				400,000
James K. Davis				51,589
John E. De B. Blockey, Trustee of the John E. de B. Blockey Living Trust dated 9/12/88				300,625
Frederick K. Ito Trust				20,340
June Y. I. Ito Trust				20,335
RP Investments, LLC				100,000
Denise J. Liszewski				23,333
Samuel Tang				4,389
Lawrence J. Taff				13,733
Kimberly F. Aquino				2,937
M.O.R. XXIX Associates Limited Partnership				148,381
M.O.R. 44 Gateway Associates Limited Partnership				1
John Parsinen				49,434
M.O.R. Commons Limited Partnership				7
John Edward De Burgh Blockey and Sanda Juanita Blockey				10,476
Lynn Hamlin				121,411
Housing Affiliates, Inc.				4,402
Reingle Corp.				730
Joseph Tawil				2,160
The Lovejoy Trust				59,528
The Century Trust				59,528
A. Charles Wilson & Betty S. Wilson Trust				5,908
Harold & Renee Holland				4,320
Irwin Hoffman				1,880
Rouse 1988 Trust				2,160
CB Management, L.L.C.				2,497
Patriot Partner, L.L.C.				25,000
National Prostate Cancer Coalition				400
John A. Luetkemeyer, Jr.				38,954
Lawrence G. Rief				2,526
Arthur Ashe Youth Tennis & Education				300
Heritage Foundation				200
Volunteers in Medicine				500
David D. Jenkins				262,165
TRC Associates Limited Partnership										352,000
				53,297,559		2,200,000		2,000,000		352,000		3,390,000		531,667