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

Exhibit 10.1

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

THIS EIGHTEENTH AMENDMENT (this “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 18, 2005, 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 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, the 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/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇, ▇▇.
	Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇, ▇▇.
	Title: Executive Vice President

Exhibit 1

Schedule of Partners

		Common Units of Partnership Units		Series E Preferred Units		Series F Preferred Units		Series G Preferred Units		Series H Preferred Units		Series I Preferred Units
General Partner
Corporate Office Properties Trust		34,979,382		1,150,000		1,425,000		2,200,000		2,000,000
Limited Partners and Preferred Limited Partners
▇▇▇ ▇. ▇▇▇▇▇▇▇		452,878
▇▇▇▇▇▇▇ Equities, L.P.		2,995,439
▇▇▇▇ ▇. ▇▇▇▇▇▇, III		566,492
LBCW Limited Partnership		3,031,107
▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇		414,910
▇▇▇▇▇ ▇. ▇▇▇▇▇		51,589
▇▇▇▇ ▇. De ▇. ▇▇▇▇▇▇▇, Trustee of the ▇▇▇▇ ▇. de ▇. ▇▇▇▇▇▇▇ Living Trust dated 9/12/88		300,625
▇▇▇▇▇▇▇▇▇ ▇. ▇▇▇ Trust		29,140
June ▇. ▇. ▇▇▇ Trust		29,135
RP Investments, LLC		150,000
▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇		28,333
▇▇▇▇▇▇ ▇▇▇▇		4,389
▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇		13,733
▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇		2,937
M.O.R. XXIX Associates Limited Partnership		148,381
M.O.R. 44 Gateway Associates Limited Partnership		1
▇▇▇▇ ▇▇▇▇▇▇▇▇		90,000
M.O.R. Commons Limited Partnership		7
▇▇▇▇ ▇▇▇▇▇▇ ▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇▇ and Sanda ▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇		10,476
▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇▇		90,905
▇▇▇▇ ▇▇▇▇▇▇		121,411
▇▇▇▇▇▇▇ School		200
National Prostate Cancer Coalition		400
The Episcopal Academy		250
University of Pennsylvania, Friends of Penn Tennis		400
Housing Affiliates, Inc.		4,402
Reingle Corp.		730
▇▇▇▇▇▇ ▇▇▇▇▇		2,160
The ▇▇▇▇▇▇▇ Trust		59,528
The Century Trust		59,528
A. ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ & ▇▇▇▇▇ ▇. ▇▇▇▇▇▇ Trust		5,908
▇▇▇▇▇▇ & ▇▇▇▇▇ ▇▇▇▇▇▇▇		4,320
▇▇▇▇▇ ▇▇▇▇▇▇▇		1,880
▇▇▇▇ & ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ Revocable Trust		2,160
▇▇▇▇▇ 1988 Trust		2,160
TRC Associates Limited Partnership												352,000
		43,655,296		1,150,000		1,425,000		2,200,000		2,000,000		352,000