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                                                                   Exhibit 10.19

                    TWELFTH AMENDMENT TO AMENDED AND RESTATED
                        AGREEMENT OF LIMITED PARTNERSHIP
                                       OF
                     BRANDYWINE OPERATING PARTNERSHIP, L.P.

                  THIS TWELFTH AMENDMENT, dated February 27, 2004 (this
"Amendment"), amends and supplements the Amended and Restated Agreement of
Limited Partnership Agreement (as heretofore amended and supplemented to date,
the "Partnership Agreement") of BRANDYWINE OPERATING PARTNERSHIP, L.P., a
Delaware limited partnership (the "Partnership"). Capitalized terms used herein
but not defined herein shall have the meanings given to such terms in the
Partnership Agreement.

                                   BACKGROUND
                                   ----------

         I. Pursuant to the Partnership Agreement, Brandywine Realty Trust (the
"General Partner"), as the general partner of the Partnership, has the power and
authority to issue additional Partnership Interests and Units in one or more
newly created classes of Partnership Interests to persons on such terms and
conditions as the General Partner may deem appropriate.

         J. The General Partner, pursuant to the exercise of such power and
authority and in accordance with the Partnership Agreement, has determined to
execute this Amendment to the Partnership Agreement to create a new class of
Partnership Interests designated as the Series E Preferred Mirror Units having
designations, preferences and other rights which are substantially the same as
the economic rights of the 7.375% Series D Senior Cumulative Redeemable
Preferred Shares of Beneficial Interest of the General Partner (the "Series D
Preferred Shares") and to evidence the issuance of such additional Partnership
Interests to the General Partner in exchange for the General Partner's
contribution to the Partnership of the net proceeds of the sale of the Series D
Preferred Shares.

                  NOW, THEREFORE, in consideration of the mutual covenants and
agreements herein contained and other good and valuable consideration, the
receipt, adequacy and sufficiency of which are hereby acknowledged, the parties
hereto, intending to be legally bound, hereby amend the Partnership Agreement as
follows:

                  1. In accordance with the Partnership Agreement, the
Partnership Agreement is hereby amended to establish, and to issue to the
General Partner, the Series E Preferred Mirror Units having the designations,
preferences and other rights set forth below:

                         (i)   Designation and Number. A class of Partnership
                               Interests designated as Series E Preferred Mirror
                               Units is hereby established. The number of Series
                               E Preferred Mirror Units shall be 2,760,000. The
                               stated value of each Series E Preferred Mirror
                               Unit shall be $25.00 (the "Stated Value").






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                         (ii)  Rank. The Series E Preferred Mirror Units will,
                               with respect to distribution rights and rights
                               upon liquidation, dissolution or winding up of
                               the Partnership, rank (a) senior to the Class A
                               Units and all Partnership Interests ranking
                               junior to the Series E Preferred Mirror Units;
                               (b) on a parity with the Partnership Interests
                               designated as Series A Preferred Mirror Units,
                               the Partnership Interests designated as Series B
                               Preferred Units, the Partnership Interests
                               designated as Series D Preferred Mirror Units and
                               all Partnership Interests issued by the
                               Partnership after the date of this Amendment the
                               terms of which specifically provide that such
                               Partnership Interests rank on a parity with the
                               Series E Preferred Mirror Units; and (c) junior
                               to all Partnership Interests issued by the
                               Partnership the terms of which specifically
                               provide that such Partnership Interests rank
                               senior to the Series E Preferred Mirror Units.

                         (iii) Distributions.

                               (A) Pursuant to Section 6.1 of the Partnership
                                   Agreement, holders of Series E Preferred
                                   Mirror Units shall be entitled to receive,
                                   out of funds legally available therefor,
                                   cumulative quarterly cash distributions equal
                                   to the amount of the cumulative quarterly
                                   cash distributions payable on the Series D
                                   Preferred Shares. Such distributions shall be
                                   payable quarterly in arrears on or before the
                                   date on which distributions on the Series D
                                   Preferred Shares are payable (each a "Series
                                   E Preferred Mirror Unit Distribution Payment
                                   Date").

                               (B) No distributions on Series E Preferred Mirror
                                   Units shall be authorized or paid or set
                                   apart for payment by the Partnership at such
                                   time as the terms and provisions of any
                                   agreement of the Partnership, including any
                                   agreement relating to its indebtedness,
                                   prohibits such authorization, payment or
                                   setting apart for payment or provides that
                                   such authorization, payment or setting apart
                                   for payment would constitute a breach
                                   thereof, or a default thereunder, or if such
                                   authorization or payment shall be restricted
                                   or prohibited by law.

                               (C) Notwithstanding the foregoing, distributions
                                   with respect to the Series E Preferred Mirror
                                   Units will accrue whether or not the terms
                                   and provisions set forth in Section 1(c)(ii)
                                   at any time prohibit the current payment of
                                   distributions, whether or not there are funds
                                   legally available for such distributions and
                                   whether or not such distributions are
                                   authorized. Accrued but unpaid distributions
                                   on the Series E Preferred Mirror Units will
                                   accumulate as of the Series E Preferred
                                   Mirror Unit Distribution Payment Date on
                                   which they first become payable.



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                               (D) When distributions are not paid in full (or a
                                   sum sufficient for such full payment is not
                                   so set apart) upon the Series E Preferred
                                   Mirror Units and any other Partnership
                                   Interests ranking on a parity as to
                                   distributions with the Series E Preferred
                                   Mirror Units, including the Series A
                                   Preferred Mirror Units, the Series B
                                   Preferred Units, and the Series D Preferred
                                   Mirror Units, all distributions authorized
                                   upon the Series E Preferred Mirror Units and
                                   any other Partnership Interests ranking on a
                                   parity as to distributions with the Series E
                                   Preferred Mirror Units shall be authorized
                                   pro rata so that the amount of distributions
                                   authorized per Partnership Unit of Series E
                                   Preferred Mirror Units and such other
                                   Partnership Interests shall in all cases bear
                                   to each other the same ratio that accrued
                                   distributions per Partnership Unit on the
                                   Series E Preferred Mirror Units and such
                                   other Partnership Interests (which shall not,
                                   with respect to such other Partnership
                                   Interests, include any accrual in respect of
                                   unpaid distributions for prior distribution
                                   periods if such other Partnership Interests
                                   do not have a cumulative distribution) bear
                                   to each other. Any distribution payment or
                                   payments on Series E Preferred Mirror Units
                                   which may be in arrears shall accrue
                                   distributions at the rate of 7.375% per
                                   annum.

                               (E) Except as provided in Section 1(c)(iv),
                                   unless full cumulative distributions on the
                                   Series E Preferred Mirror Units have been or
                                   contemporaneously are authorized and paid or
                                   authorized and a sum sufficient for the
                                   payment thereof is set apart for payment for
                                   all past distribution periods and the then
                                   current distribution period, no distributions
                                   (other than in Partnership Interests ranking
                                   junior to the Series E Preferred Mirror Units
                                   as to distributions and upon liquidation,
                                   dissolution or winding up) shall be
                                   authorized or paid or set aside for payment
                                   nor shall any other distribution be
                                   authorized or made upon the Class A Units,
                                   the Series A Preferred Mirror Units, the
                                   Series B Preferred Units, the Series D
                                   Preferred Mirror Units or any other
                                   Partnership Interests ranking junior to or on
                                   a parity with the Series E Preferred Mirror
                                   Units as to distributions or upon
                                   liquidation, dissolution or winding up, nor
                                   shall any Class A Units, Series A Preferred
                                   Mirror Units, Series B Preferred Units,
                                   Series D Preferred Mirror Units or any other
                                   Partnership Interests ranking junior to or on
                                   a parity with the Series E Preferred Mirror



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                                   Units as to distributions or upon liquidation
                                   be redeemed, purchased or otherwise acquired
                                   for any consideration (or any moneys be paid
                                   to or made available for a sinking fund for
                                   the redemption of any such units or other
                                   Partnership Interests) by the Partnership or
                                   any other entity controlled directly or
                                   indirectly by the Partnership (except by
                                   conversion into or exchange for Partnership
                                   Interests ranking junior to the Series E
                                   Preferred Mirror Units as to distributions
                                   and upon liquidation, dissolution or winding
                                   up).

                               (F) Holders of the Series E Preferred Mirror
                                   Units shall not be entitled to any
                                   distribution, whether payable in cash,
                                   property or Partnership Units in excess of
                                   full cumulative distributions on the Series E
                                   Preferred Mirror Units as described above.
                                   Any distribution payment made on the Series E
                                   Preferred Mirror Units shall first be
                                   credited against the earliest accrued but
                                   unpaid distribution due with respect to such
                                   Series E Preferred Mirror Units which remains
                                   payable.

                         (iv)  Liquidation Preference.

                               (A) Upon any voluntary or involuntary
                                   liquidation, dissolution or winding up of the
                                   affairs of the Partnership, the holders of
                                   Series E Preferred Mirror Units then
                                   outstanding are entitled to be paid out of
                                   the assets of the Partnership available for
                                   distribution to the Partners pursuant to
                                   Section 13.5(a) of the Partnership Agreement
                                   a liquidation preference equal to the Stated
                                   Value per Series E Preferred Mirror Unit,
                                   plus an amount equal to any accrued and
                                   unpaid distributions to the date of payment,
                                   before any distribution of assets is made to
                                   holders of Class A Units and GP Units or any
                                   other Partnership Interests that rank junior
                                   to the Series E Preferred Mirror Units upon
                                   liquidation, dissolution or winding up.

                               (B) In the event that, upon any such voluntary or
                                   involuntary liquidation, dissolution or
                                   winding up, the available assets of the
                                   Partnership are insufficient to pay the
                                   amount of the liquidating distributions on
                                   all outstanding Series E Preferred Mirror
                                   Units and the corresponding amounts payable
                                   on all other Partnership Interests ranking on
                                   a parity with the Series E Preferred Mirror
                                   Units in the distribution of assets,
                                   including the Series A Preferred Mirror
                                   Units, the Series B Preferred Units and the
                                   Series D Preferred Mirror Units, then such
                                   assets shall be allocated among the Series E
                                   Preferred Mirror Units, as a class, and each
                                   class or series of such other such
                                   Partnership Interests, as classes, in
                                   proportion to the full liquidating
                                   distributions to which they would otherwise
                                   be respectively entitled.



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                               (C) After payment of the full amount of the
                                   liquidating distributions to which they are
                                   entitled, the holders of Series E Preferred
                                   Mirror Units will have no right or claim to
                                   any of the remaining assets of the
                                   Partnership.

                               (D) The consolidation or merger of the
                                   Partnership with or into any other
                                   partnership, limited liability company,
                                   corporation, trust or entity or of any other
                                   partnership, limited liability company,
                                   corporation, trust or other entity with or
                                   into the Partnership, or the sale, lease or
                                   conveyance of all or substantially all of the
                                   property or business of the Partnership,
                                   shall not be deemed to constitute a
                                   liquidation, dissolution or winding up of the
                                   Partnership for purposes of this Section
                                   1(d).

                         (v)   Redemption. In connection with a redemption by
                               the General Partner of any or all of the Series D
                               Preferred Shares, the Partnership shall provide
                               cash to the General Partner for such purpose
                               which shall be equal to the redemption price
                               (including accrued and unpaid distributions) of
                               the Series D Preferred Shares to be redeemed and
                               in exchange one Series E Preferred Mirror Unit
                               shall be canceled with respect to each Series D
                               Preferred Share so redeemed. From and after the
                               date on which the Series D Preferred Shares are
                               redeemed, the Series E Preferred Mirror Units so
                               canceled shall no longer be outstanding and all
                               rights hereunder, to distributions or otherwise,
                               with respect to such Series E Preferred Mirror
                               Units shall cease.

                         (vi)  Allocations. Allocations of the Partnership's
                               items of income, gain, loss and deduction shall
                               be allocated among holders of Series E Preferred
                               Mirror Units in accordance with Article VII of
                               the Partnership Agreement.

                  2. Subparagraph (g) of Section 7.2 of the Partnership
Agreement is amended and restated in its entirety as follows:

                         (g) Priority Allocation. All or a portion of the Net
Income of the Partnership for the Fiscal Year, if any, shall be specially
allocated to the Partners holding Series A Preferred Mirror Units, Series B
Preferred Units, Series D Preferred Mirror Units and Series E Preferred Mirror
Units in proportion to the cumulative distributions each has received pursuant
to Sections 6.1, 6.2, and 13.5 hereof and, with respect to the Partners holding
Series A Preferred Mirror Units, Section 1(c) and 1(d) of the Fourth Amendment
to this Agreement or, with respect to Partners holding Series B Preferred Units,
Section 1.C and 1.D of the Fifth Amendment to this Agreement or, with respect to




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the Partners holding Series D Preferred Mirror Units, Section 1(c) and 1(d) of
the Eleventh Amendment to this Agreement or, with respect to the Partners
holding Series E Preferred Mirror Units, Section 1(c) and 1(d) of the Twelfth
Amendment to this Agreement, from the commencement of the Partnership to the end
of such Fiscal Year, in an amount equal to the excess, if any, of the sum of (i)
the aggregate Net Loss allocated to such Partners pursuant to Section 7.1(b)
hereof for all prior Fiscal Years, if any, and (ii) the aggregate distributions
received by such Partners pursuant to Sections 6.1, 6.2, and 13.5 hereof and,
with respect to Partners holding Series A Preferred Mirror Units, Section 1(c)
and 1(d) of the Fourth Amendment to this Agreement or, with respect to Partners
holding Series B Preferred Units, Section 1.C and 1.D of the Fifth Amendment to
this Agreement or, with respect to Partners holding Series D Preferred Mirror
Units, Section 1(c) and 1(d) of the Eleventh Amendment to this Agreement or,
with respect to Partners holding Series E Preferred Mirror Units, Section 1(c)
and 1(d) of the Twelfth Amendment to this Agreement, from the commencement of
the Partnership to the end of such Fiscal Year, over the aggregate items of Net
Income allocated to such Partners pursuant to this Section 7.2(g) for all prior
Fiscal Years.

                  3. Except as expressly set forth in this Amendment to the
Partnership Agreement, the Partnership Agreement is hereby ratified and
confirmed in each and every respect.

                  IN WITNESS WHEREOF, this Twelfth Amendment to the Amended and
Restated Agreement of Limited Partnership of Brandywine Operating Partnership,
L.P. has been executed and delivered as of the date first above written.

                               GENERAL PARTNER:

                               BRANDYWINE REALTY TRUST

                               By:______________________________________________
                                  Name: Gerard H. Sweeney
                                  Its:  President and Chief Executive Officer













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