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

  	
   

  



 











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