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Exhibit 10.1


Twelfth Amendment
To
Second Amended and Restated
Limited Partnership Agreement
Of
Corporate Office Properties, L.P.

        This Twelfth 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 June 2, 2003, 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 (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/  ROGER A. WAESCHE, JR.      
Roger A. Waesche, Jr.
 Senior Vice President


Schedule of Partners

General Partner
   Partnership Units
Corporate Office Properties Trust   27,082,879

Limited Partners and Preferred Limited Partners
 
 
Jay H. Shidler   452,878
Shidler Equities, L.P.   2,995,439
Clay W. Hamlin, III   568,492
LBCW Limited Partnership   3,161,427
Robert L. Denton   434,910
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
Henry D. Bullock   76,533
Frederick K. Ito Trust   29,140
June Y. I. Ito Trust   29,135
RP Investments, LLC   268,671
Denise J. Liszewski   34,333
Samuel Tang   22,889
Lawrence J. Taff   13,733
Kimberly F. Acquino   5,874
M.O.R. XXIX Associates Limited Partnership   148,381
M.O.R. 44 Gateway Associates Limited Partnership   1
John Parsinen   90,000
M.O.R. Commons Limited Partnership   7
John Edward De Burgh Blockey and Sanda Juanita Blockey   50,476
Anthony Muscatello   90,905
Lynn Hamlin   121,411
    36,029,748
   


EXHIBIT 1

Addendum

Series
Preferred
Units
   Preferred
Limited Partner
   No. of
Preferred
Units
   Liquidation
Preference
Per Preferred
Unit
   Priority
Percentage
Return*
   Priority
   Conversion
Factor
   Conversion
Commencement
Date
B   General Partner   1,250,000   $ 25   2.50 % Senior   None   N/A
C   UPG   1,016,662   $ 25   **   Senior   2.381   12/22/2000
D   General Partner   544,000   $ 25   1.00 % Senior   ***   ***
E   General Partner   1,150,000   $ 25   2.5625 % Senior   None   N/A
F   General Partner   1,425,000   $ 25       Senior   None   N/A
*
Priority Return Percentage is expressed as a percentage of the Liquidation Preference per Distribution Period. See the Agreement for the definitions of "Priority Return Percentage," "Liquidation Preference" and "Distribution Period."

**
Priority Percentage Return for the Series C Preferred Units shall be:
***
With respect to any series of Preferred Units issued to the General Partner pursuant to Section 4.2(B) of the Agreement, the Conversion Commencement Date and the applicable Conversion Factor shall correspond to the conversion commencement date and conversion factor of the related issuance of securities by the General Partner as provided in Section 4.2(B) of the Agreement. See Section 9.8(A)(1) of the Agreement.


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Twelfth Amendment To Second Amended and Restated Limited Partnership Agreement Of Corporate Office Properties, L.P.
Schedule of Partners
EXHIBIT 1 Addendum