FIRST AMENDMENT TO OPTION AGREEMENT

     THIS FIRST AMENDMENT TO OPTION AGREEMENT ("Amendment") is made and executed
as of this 22nd day of June, 1998 by and between NBP-III, LLC ("Seller") and
CORPORATE OFFICE PROPERTIES, L.P., its successors and assigns ("Buyer").

     A.   Seller and Buyer entered into an Option Agreement dated May 14, 1988
pursuant to which Seller granted to Buyer the option to purchase the Property
known as Lot 11 of the National Business Park on which Seller intends to develop
and construct an office building containing approximately 110,000 gross square
feet (now planned for 90,000 gross square feet) to be known as 134 National
Business Park (the "Option Agreement").  Capitalized terms used, but not
defined, in this Amendment shall have the meanings set forth in the Option
Agreement.

     B.   By notice dated May 28, 1998, Buyer exercised its option to purchase
the Property.

     C.   Seller and Buyer desire to amend the Option Agreement as set forth in
this Amendment.

     NOW, THEREFORE, in consideration of the agreements contained herein and
intending to be legally bound hereby, Seller and Buyer agree as follows:

          1.   The first sentence of Section 1 of the Option Agreement is hereby
deleted, and the following sentence is substituted in its place:  "The Purchase
Price for the Property shall be determined as of the date of "Settlement"
(hereinafter defined) and shall be that sum which is equal to the "Seller's Book
Value" (hereinafter defined) of the Property, not to exceed $12,287,130.00 as
set forth on the attached Exhibit "Construction Budget" attached hereto assuming
that the building of 90,000 gross square feet to be constructed on the Property
is fully completed."

          2.   The following sentence is hereby added at the end of Section 1 of
the Option Agreement:  "The Construction Budget shown in Exhibit "Construction
Budget" shall not be increased by more than $50,000.00 without Buyer's prior
written consent.



          3.   The following Section 9(d) is added to the Option Agreement:

               "(d) Seller shall have paid all costs of any nature relating to
                    the ownership, development and construction of the buildings
                    and improvements on the Property through the date of
                    Settlement and shall deliver evidence of such payment to
                    Buyer.  Seller shall execute and deliver, and shall cause
                    all contractors to execute and deliver, all documents
                    reasonably required to effectuate Buyer's takeover of the
                    responsibility for such construction, free and clear of any
                    pre-Settlement obligations or claims, which documents shall
                    be reasonably acceptable to Seller and Buyer."

          4.   Exhibit "Construction Budget" attached hereto and made a part
hereof is hereby attached to and made part of the Option Agreement.

          5.   As amended by this Amendment, the Option Agreement shall remain
in full force and effect.



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     IN WITNESS WHEREOF, Seller and Buyer have executed this Amendment on the
day and year first above written.

WITNESS:                           CORPORATE OFFICE PROPERTIES, L.P., by its
                                   sole general partner, Corporate Office
                                   Properties Trust


            /s/               By:  /s/ CLAY W. HAMLIN, III
- ---------------------------        -----------------------
                                   Clay W. Hamlin, III
                                   President and Chief Executive Officer


WITNESS:                           NBP-III, LLC, a Maryland limited liability
                                   company, by CPI National Business Park-III,
                                   Inc., a Maryland corporation, authorized
                                   Member


            /s/               By:  /s/ ROGER A. WAESCHE, JR.
- ---------------------------        -------------------------
                                   Roger A. Waesche, Jr.
                                   Vice President


ASSENTED AND AGREED TO BY
CONSTELLATION PROPERTIES, INC.


By:            /s/
     ----------------------
     Vice President


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