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                                 Exhibit 10-12


                 PRENTISS PROPERTIES ACQUISITION PARTNERS, L.P.

                   Thirteenth Amendment to the Second Amended
                and Restated Agreement of Limited Partnership of
                 Prentiss Properties Acquisition Partners, L.P.,
                      Establishing the Series D Cumulative
              Convertible Redeemable Preferred Units of Partnership
                      Interest and Fixing Distribution and
                   Other Preferences and Rights of Such Units

                                    RECITALS

         A. The Board of Trustees of Prentiss Properties Trust (the "Trust") has
adopted a resolution designating and classifying 3,773,585 unissued and
unclassified preferred shares of beneficial interest of the Trust as Series D
Cumulative Convertible Redeemable Preferred Shares of Beneficial Interest (the
"SERIES D PREFERRED SHARES").

         B. Pursuant to Section 4.02 and Article XI of the Second Amended and
Restated Agreement of Limited Partnership (the "AGREEMENT") of Prentiss
Properties Acquisition Partners, L.P. (the "Partnership"), Prentiss Properties
I, Inc. as the sole general partner of the Partnership (the "General Partner"),
desires to amend the Agreement to establish the Series D Cumulative Convertible
Redeemable Preferred Units of Partnership Interest (the "SERIES D PREFERRED
UNITS") with economic interests substantially similar to those of the Series D
Preferred Shares.

         NOW, THEREFORE, the General Partner hereby adopts the following
amendment to the Partnership Agreement:

         I.    AMENDMENT TO SECTION 4.02 (d). Section 4.02(d) is deleted in its
entirety.

         II.   AMENDMENT TO SECTION 4.02. Section 4.02 is amended by adding
Section 4.02(g), as follows:

(g)      Series D Cumulative Convertible Redeemable Preferred Units of
Partnership Interest.

         Section 1.  DEFINITIONS. For purposes of the Series D Preferred Units,
the following terms shall have the meanings indicated:

                     "Applicable Treasury Rate," for each Dividend Period, shall
mean the annual yield to maturity to U.S. Treasury securities with a ten-year
maturity, as compiled by and published in the most recent Federal Reserve
Statistical Release H.13(519) which has become publicly available prior to the
last Business Day of such Dividend Period (or, if such Statistical Release is no
longer published, any publicly available source of similar date).

                     "Base Rate" shall mean an annual dividend payment in an
amount per share equal to $1.60; PROVIDED, HOWEVER, that if the Trust gives
notice of its election to make a Dividend Increase (as defined in the Exchange
Agreement) following a Change of Control (as defined in the Exchange Agreement)
in accordance with Section 6.7 of the Exchange Agreement, then from and after
the date of such notice, the "Base Rate" shall mean an annual dividend payment
in an
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amount per share equal to the product of (a) the greater of (1) 800 basis points
plus the Applicable Treasury Rate or (2) 12% and (b) the greater of (1) the
Liquidation Preference per Series D Preferred Share and (2) the Volume-Weighted
Average trading Price for the thirty trading days preceding the Change of
Control transaction of the number of Common Shares into which each Series D
Preferred Share is then convertible.

                     "Board of Trustees" shall mean the Board of Trustees of the
Trust.

                     "Business Day" shall mean any day, other than a Saturday or
Sunday, that is neither a legal holiday nor a day on which banking institutions
in New York City, New York are authorized or required by law, regulation or
executive order to close.

                     "Call Date" shall mean the date specified in the notice to
holders required under Section 5(d) as the Call Date.

                     "Change of Control" shall have the meaning set forth in
Section 6.7(f) of the Exchange Agreement.

                     "Code" shall mean the Internal Revenue Code of 1986, as
amended.

                     "Common Units" shall mean all the units of partnership
interest in the Partnership that are not specifically designated as preferred
units pursuant to Section 4.02.

                     "Constituent Person" shall have the meaning set forth in
Section 6(e).

                     "Conversion Date" shall have the meaning set forth in
Section 6(a).

                     "Conversion Price" shall mean the conversion price per
Common Unit for which the Series D Preferred Units are convertible, as such
Conversion Price maybe adjusted pursuant to Section 6. The initial conversion
price shall be $26.50.

                     "Current Market Price" of publicly traded Common Units or
any other Partnership Units or other security of the Partnership or any other
issuer for any day shall mean the last reported sales price, regular way, on
such day, or, if no sale takes place on such day, the average of the reported
closing bid and asked prices on such day, regular way, in either case as
reported on the New York Stock Exchange ("NYSE") or, if such security is not
listed or admitted for trading on the NYSE, on the principal national securities
exchange on which such security is listed or admitted for trading or, if not
listed or admitted for trading on any national securities exchange, on the
Nasdaq National Market ("NASDAQ") or, if such security is not quoted on NASDAQ,
the average of the closing bid and asked prices on such day in the
over-the-counter market as reported by the National Association of Securities
Dealers, Inc. (the "NASD") or, if bid and asked prices for such security on such
day shall not have been reported through the NASD, the average of the bid and
asked prices on such day as furnished by any NYSE member firm regularly making a
market in such security selected for such purpose by the Board of Trustees. If
the Common Units are not publicly traded, then the Current Market Price of such
Common Units shall be equal to the Current Market Price of common shares of
beneficial interest of the Trust ("COMMON SHARES"), multiplied by the
then-current Conversion Factor.

                     "Distribution Payment Date" shall mean (i) for any
Distribution Period with respect to which the Partnership pays a distribution on
the Common Units, the date on which such distribution is paid, or (ii) for any
Distribution Period with respect to' which the Partnership

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does not pay a distribution on the Common Units, a date to be set by the General
Partner, which date shall not be later than the thirtieth calendar day after the
end of the applicable Distribution Period.

                     "Distribution Periods" shall mean quarterly distribution
periods commencing on January 1, April 1, July 1 and October 1 of each year and
ending on and including the day preceding the first day of the next succeeding
Distribution Period with respect to any Series D Preferred Units (other than the
initial Distribution Period, which shall commence on the Issue Date for such
Series D Preferred Units and end on and include the last day of the calendar
quarter immediately following such Issue Date, and other than the Distribution
Period during which any Series D Preferred Units shall be redeemed pursuant to
Section 5 or converted pursuant to Section 6, which shall end on and include the
Call Date with respect to the Series D Preferred Units being redeemed or the
date that such Series D Preferred Units are converted, as the case may be).

                     "Exchange Agreement" shall mean the Exchange Agreement
,dated as of March 20, 2001, by and among Security Capital Preferred Growth
Incorporated, a Maryland corporation, the Trust and the Operating Partnership,
as amended from time to time.

                     "Expiration Time" shall have the meaning set forth in
Section 6(d)(iv).

                     "Fair Market Value" shall mean the average of the daily
Current Market Prices of a Common Unit on the five (5) consecutive Trading Days
selected by the General partner commencing not more than 20 Trading Days before,
and ending not later than, the earlier of the day in question and the day before
any "ex date" with respect to the issuance or distribution requiring such
computation. The term "ex date," when used with respect to any issuance or
distribution, means the first day on which the Common Units trade regular way,
without the right to receive such issuance or distribution, on the exchange or
in the market, as the case may be, used to determine that day's Current Market
Price.

                     "Fully Junior Units" shall mean the Common Units and any
other class or series of units of partnership interest in the Partnership now or
hereafter issued and outstanding over which the Series D Preferred Units have
preference or priority in both (i) the payment of distributions and (ii) the
distribution of assets on any liquidation, dissolution or winding up of the
Trust.

                     "Funds from Operations" shall mean net income (loss)
(computed in accordance with generally accepted accounting principles) excluding
gains (or losses) from debt restructuring, and distributions in excess of
earnings allocated to other minority interests (as reflected in the financial
statements of the Partnership) plus depreciation/amortization of assets unique
to the real estate industry, all computed in a manner consistent with the
revised definition of Funds From Operations adopted by the National Association
of Real Estate Investment Trusts ("NAREIT"), in its White Paper dated March
1995, as such definitions may be modified from time to time, as determined by
the General Partner in good faith.

                     "Issue Date" shall mean the date on which the Series D
Preferred Units are issued.

                     "Junior Units" shall mean the Common Units and any other
class or series of Partnership Units now or hereafter issued and outstanding
over which the Series D Preferred

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Units have preference or priority in the payment of distributions or in the
distribution of assets on any liquidation, dissolution or winding up of the
Trust.

                     "Non-Electing Unit" shall have the meaning set forth in
Section 6(e).

                     "Parity Preferred Units" shall have the meaning set forth
in Section 7(b).

                     "Person" shall mean any individual, firm, partnership,
corporation, limited liability company, trust or other entity, and shall include
any successor (by merger or otherwise) of such entity.

                     "Purchased Units" shall have the meaning set forth in
Section 6(d)(iv).

                     "REIT Termination Event" shall mean the earliest to occur
of:

                     (i)   the filing of a federal income tax return by the
                           Trust for any taxable year on which the Trust does
                           not compute its income as a real estate investment
                           trust;

                     (ii)  the approval by the unitholders of the Trust of a
                           proposal for the Trust to cease to qualify as a real
                           estate investment trust;

                     (iii) a determination by the Board of Trustees of the
                           Trust, based on the advice of counsel, that the Trust
                           has ceased to qualify as a real estate investment
                           trust; or

                     (iv)  a "determination" within the meaning of Section
                           1313(a) of the Code that the Trust has ceased to
                           qualify as a real estate investment trust.

                     "Securities" and "Security" shall have the meanings set
forth in Section 6(d)(iii).

                     "Securities Act" shall mean the Securities Act of 1933, as
amended.

                     "Series D Preferred Units" shall have the meaning given
such term in the preamble to this Thirteenth Amendment.

                     "Set apart for payment" shall be deemed to include, without
any action other than the following, the recording by the Partnership in its
accounting ledgers of any accounting or bookkeeping entry which indicates,
pursuant to a declaration or other action of the General Partner, the allocation
of funds to be so paid on any series or class of Partnership Units of the Trust;
PROVIDED, HOWEVER, that if any funds for any class or series of Junior Shares or
any class or series of shares of beneficial interest ranking on a parity with
the Series D Preferred Units as to the payment of distributions are placed in a
separate account of the Trust or delivered to a disbursing, paying or other
similar agent, then "set apart for payment" with respect to the Series D
Preferred Units shall mean placing such funds in a separate account or
delivering such funds to a disbursing, paying or other similar agent.

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                     "Trading Day" shall mean any day on which the securities in
question are traded on the NYSE, or if such securities are not listed or
admitted for trading on the NYSE, on the principal national securities exchange
on which such securities are listed or admitted, or if not listed or admitted
for trading on any national securities exchange, on NASDAQ, or if such
securities are not quoted on NASDAQ, in the securities market in which the
securities are traded.

                     "Transaction" shall have the meaning set forth in Section
6(e).

                     "Transfer Agent" shall mean the Trust, or such other agent
or agents of the Trust as may be designated by the Board of Trustees or their
designee as the transfer agent, registrar and distribution disbursing agent for
the Series D Preferred Units.

                     "Volume-Weighted Average Trading Price" shall mean, for any
period, the number obtained by dividing (i) the sum of the products, for each
sale of any security during such period, of (a) the sale price of such security,
regular way, as reported in the principal consolidated transaction reporting
system with respect to securities listed or admitted to trading on the NYSE or,
if the securities are not listed or admitted to trading on the NYSE, as reported
in the principal consolidated transaction reporting system with respect to
securities listed on the principal national securities exchange on which the
securities are admitted to trading or, if the securities are not listed or
admitted to trading on any national securities exchange, the sale price, as
reported by the National Association of Securities Dealers, Inc. Automated
Quotation System or, if such system is no longer in use, the principal other
automated quotation system that may then be in use or, if the securities are not
quoted by any such organization, the sales prices as furnished by professional
market makers making a market in the securities or, if the securities are not
publicly traded, the sale price as reasonably determined in good faith by the
Board of Trustees and (b) the number of such securities sold by (ii) the total
number of such securities sold during such period.

Capitalized terms not otherwise defined herein have the meanings ascribed to
them in the Partnership Agreement.

         Section 2.  NUMBER OF UNITS AND DESIGNATION. A series of preferred
units of partnership interest designated as Series D Cumulative Convertible
Redeemable Preferred Units of Partnership Interest is hereby established and the
number of units which shall constitute such series shall not be more than
3,773,585 units, which number may be decreased (but not below the aggregate
number thereof then outstanding and/or which have been reserved for issuance)
from time to time by the General Partner.

         Section 3.  DISTRIBUTIONS.

                (a)  Subject to the preferential rights of the holders of Parity
         Preferred Units and holders of any preferred units that rank senior in
         the payment of distributions to the Series D Preferred Units issued
         after the date hereof in accordance herewith as to payment of
         distributions and rights upon voluntary or involuntary dissolution,
         liquidation or winding up, the holders of Series D Preferred Units
         shall be entitled to receive, when, as and if determined by the General
         Partner in its sole discretion, out of finds legally available for the
         payment of distributions, cumulative preferential distributions payable
         in

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         cash in an amount per share equal to the greater of (i) the Base Rate
         or (ii) the regular cash distributions (determined on each Distribution
         Payment Date) on the Common Units, or portion thereof, into which a
         Series D Preferred Share is convertible. The distributions referred to
         in clause (ii) of the preceding sentence shall equal the number of
         Common Units, or portion thereof, into which one Series D Preferred
         Unit will be convertible on or after the Conversion Date, multiplied by
         the most current quarterly distribution on one Common Unit on or before
         the applicable Distribution Payment Date. If the Partnership pays a
         regular cash distribution on the Common Units with respect to a
         Distribution Period after the date on which the Distribution Payment
         Date is declared pursuant to clause (ii) of the definition of
         Distribution Payment Date and the distribution calculated pursuant to
         clause (ii) of this paragraph (a) with respect to such Distribution
         Period is greater than the distribution previously declared on the
         Series D Preferred Units with respect to such Distribution Period, the
         Partnership shall pay an additional distribution to the holders of the
         Series D Preferred Units on the date on which the distribution on the
         Common Units is paid, in an amount equal to the difference between (y)
         the distribution calculated pursuant to clause (ii) of this paragraph
         (a) and (z) the amount of distributions previously declared on the
         Series D Preferred Units with respect to such Distribution Period. The
         distributions shall begin to accrue and shall be fully cumulative from
         the first day of the applicable Distribution Period, whether or not in
         any Distribution Period or Periods there shall be funds of the
         Partnership legally available for the payment of such distributions,
         and shall be payable quarterly, when, as and if the General Partner, in
         its sole discretion, determines, in arrears on Distribution Payment
         Dates. Each such distribution shall be payable in arrears to the
         holders of record of Series D Preferred Units as they appear in the
         records of the Partnership at the close of business on such record
         dates, not less than 10 nor more than 50 days preceding such
         Distribution Payment Dates thereof, as shall be fixed by the General
         Partner. Accrued and unpaid distributions for any past Distribution
         Periods may be declared and paid at any time and for such interim
         periods, without reference to any regular Distribution Payment Date, to
         holders of record on such date, not less than 10 nor more than 50 days
         preceding the payment date thereof, as may be fixed by the General
         Partner. Any distribution payment made on Series D Preferred Units
         shall first be credited against the earliest accrued but unpaid
         distribution due with respect to Series D Preferred Units which remains
         payable.

                (b)  The amount of distributions referred to in clause (i) of
         Section 3(a) payable for each full Distribution Period on the Series D
         Preferred Units shall be computed by dividing the annual distribution
         rate by four. The initial Distribution Period for the Series D
         Preferred Units will include a partial distribution for the period from
         the Issue Date until the last day of the calendar quarter immediately
         following such Issue Date. The amount of distributions payable for such
         period, or any other period shorter than a full Distribution Period, on
         the Series D Preferred Units shall be computed by dividing the number
         of days in such period by 365 and multiplying the result by the Series
         D Preferred distribution rate determined in accordance with Section
         3(a). Holders of Series D Preferred Units shall not be entitled to any
         distributions, whether payable in cash, property or shares, in excess
         of cumulative distributions, as herein provided, on the Series D
         Preferred Units. No interest, or sum of money in lieu of interest,
         shall be payable in respect of any distribution or distributions on the
         Series D Preferred Units which may be in arrears.

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                (c)  So long as any Series D Preferred Units are outstanding, no
         distributions, except as described in the immediately following
         sentence, shall be declared or paid or set apart for payment on any
         class or series of Parity Preferred Units for any period unless full
         cumulative distributions have been or contemporaneously are declared
         and paid or declared and a sum sufficient for the payment thereof set
         apart for such payment on the Series D Preferred Units for all
         Distribution Periods terminating on or prior to the Distribution
         Payment Date on such class or series of Parity Preferred Units. When
         distributions are not paid in full or a sum sufficient for such payment
         is not set apart, as aforesaid, all distributions declared upon Series
         D Preferred Units and all distributions declared upon any other class
         or series of Parity Preferred Units shall be declared ratably in
         proportion to the respective amounts of distributions accumulated and
         unpaid on the Series D Preferred Units and accumulated and unpaid on
         such Parity Preferred Units.

                (d)  So long as any Series D Preferred Units are outstanding, no
         distributions (other than distributions paid solely in shares of, or
         options, warrants or rights to subscribe for or purchase shares of,
         Fully Junior Units) shall be declared or paid or set apart for payment
         or other distribution shall be declared or made or set apart for
         payment upon Junior Units, nor shall any Junior Units be redeemed,
         purchased or otherwise acquired (other than a redemption, purchase or
         other acquisition of Common Units made for purposes of an employee
         incentive or benefit plan of the Partnership or any subsidiary or
         affiliate) for any consideration (or any moneys be paid to or made
         available for a sinking fund for the redemption of any Junior Units) by
         the Partnership, directly or indirectly (except by conversion into or
         exchange for Fully Junior Units), unless in each case (i) the full
         cumulative distributions on all outstanding Series D Preferred Units
         and any other Parity Preferred Units of the Partnership shall have been
         or contemporaneously are declared and paid or declared and set apart
         for payment for all past Distribution Periods with respect to the
         Series D Preferred Units and all past distribution periods with respect
         to such Parity Preferred Units and (ii) sufficient funds shall have
         been or contemporaneously are declared and paid or declared and set
         apart for the payment of the distribution for the current Distribution
         Period with respect to the Series D Preferred Units and the current
         distribution period with respect to such Parity Preferred Units.

                (e)  No distributions on Series D Preferred Units shall be
         declared by the General Partner 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 declaration, payment or setting apart for
         payment or provides that such declaration, payment or setting apart for
         payment would constitute a breach thereof or a default thereunder, or
         if such declaration or payment shall be restricted or prohibited by
         law.

         Section 4.  LIQUIDATION PREFERENCE.

                     (a) In the event of any liquidation, dissolution or winding
         up of the Partnership, whether voluntary or involuntary, subject to the
         rights of holders of Parity Preferred Units and subject to the prior
         preferences and other rights of any series of Partnership Units ranking
         senior to the Series D Preferred Units of Beneficial Interest upon
         liquidation, distribution or winding up of the Partnership, before any
         payment or distribution of the

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         assets of the Partnership (whether capital or surplus) shall be made to
         or set apart for the holders of Junior Units, the holders of the Series
         D Preferred Units shall be entitled to receive Twenty Six Dollars and
         Fifty Cents ($26.50) (the "LIQUIDATION PREFERENCE") per Series D
         Preferred Unit plus an amount equal to all distributions (whether or
         not earned or declared) accrued and unpaid thereon to the date of final
         distribution to such holders; but such holders shall not be entitled to
         any further payment; PROVIDED, that the distribution payable with
         respect to the Distribution Period containing the date of final
         distribution shall be equal to the greater of (i) the distribution
         provided in Section 3(a)(i) or (ii) the distribution determined
         pursuant to Section 3(a)(ii) for the preceding Distribution Period. If,
         upon any liquidation, dissolution or winding up of the Partnership, the
         assets of the Partnership, or proceeds thereof, distributable among the
         holders of the Series D Preferred Units shall be insufficient to pay in
         full the preferential amount aforesaid and liquidating payments on any
         other shares of any class or series of Parity Preferred Units, then
         such assets, or the proceeds thereof, shall be distributed among the
         holders of Series D Preferred Units and any such other Parity Preferred
         Units ratably in accordance with the respective amounts that would be
         payable on such Series D Preferred Units and any such other Parity
         Preferred Units if all amounts payable thereon were paid in full. For
         the purposes of this Section 4, (i) a consolidation or merger of the
         Partnership with one or more partnerships, corporations, real estate
         investment trusts or other entities or (ii) a sale, lease or conveyance
         of all or substantially all of the Partnership's property or business
         shall not be deemed to be a liquidation, dissolution or winding up,
         voluntary or involuntary, of the Partnership.

                  (b)  Subject to the rights of the holders of shares of any
         series or class or classes of units ranking on a parity with or prior
         to the Series D Preferred Units upon liquidation, dissolution or
         winding up, upon any liquidation, dissolution or winding up of the
         Partnership, after payment shall have been made in full to the holders
         of the Series D Preferred Units, as provided in this Section 4, the
         holders of Series D Preferred Units shall have no other claim to the
         remaining assets of the Partnership and any other series or class or
         classes of Junior Units shall, subject to the respective terms and
         provisions (if any) applying thereto, be entitled to receive any and
         all assets remaining to be paid or distributed, and the holders of the
         Series D Preferred Units shall not be entitled to share therein.

         Section 5.  REDEMPTION AT THE OPTION OF THE PARTNERSHIP.

                     (a) The Series D Preferred Units shall not be redeemable by
         the Partnership prior to December 29, 2005. On and after December 29,
         2005, the Partnership, at its option, may redeem the Series D Preferred
         Units, in whole at any time or from time to time in part out of funds
         legally available therefor at a redemption price payable in cash equal
         to 100% of the Liquidation Preference per Series D Preferred Units
         (plus all accumulated, accrued and unpaid distributions as provided
         below).

                     (b) Upon any redemption of Series D Preferred Units
         pursuant to this Section 5, the Partnership shall pay all accrued and
         unpaid distributions, if any, thereon to the Call Date, without
         interest. If the Call Date falls after a distribution payment record
         date and prior to the corresponding Distribution Payment Date, then
         each holder of Series D

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         Preferred Units at the close of business on such distribution payment
         record date shall be entitled to the distribution payable on such
         shares on the corresponding Distribution Payment Date notwithstanding
         any redemption of such shares before such Distribution Payment Date.
         Except as provided above, the Partnership shall make no payment or
         allowance for unpaid distributions, whether or not in arrears, on
         Series D Preferred Units called for redemption.

                     (c) If full cumulative distributions on the Series D
         Preferred Units and any other class or series of Parity Preferred Units
         of the Partnership have not been declared and paid or declared and set
         apart for payment; the Series D Preferred Units may not be redeemed
         under this Section 5 in part and the Partnership may not purchase or
         acquire Series D Preferred Units, otherwise than pursuant to a purchase
         or exchange offer made on the same terms to all holders of Series D
         Preferred Units.

                     (d) Notice of the redemption of any Series D Preferred
         Units under this Section 5 shall be mailed by first-class mail to each
         holder of record of Series D Preferred Units to be redeemed at the
         address of each such holder as shown on the Partnership's records, not
         less than 30 nor more than 90 days prior to the Call Date. Neither the
         failure to mail any notice required by this paragraph (d), nor any
         defect therein or in the mailing thereof, to any particular holder,
         shall affect the sufficiency of the notice or the validity of the
         proceedings for redemption with respect to the other holders. Each such
         mailed notice shall state, as appropriate: (1) the Call Date; (2) the
         number of Series D Preferred Units to be redeemed and, if fewer than
         all the shares held by such holder are to be redeemed, the number of
         such shares to be redeemed from such holder; (3) the redemption price;
         (4) the then-current Conversion Price; and (5) that distributions on
         the shares to be redeemed shall cease to accrue on such Call Date
         except as otherwise provided herein. Notice having been mailed as
         aforesaid, from and after the Call Date (unless the Partnership shall
         fail to make available an amount of cash necessary to effect such
         redemption), (i) except as otherwise provided herein, distributions on
         the Series D Preferred Units so called for redemption shall cease to
         accrue, (ii) such shares shall no longer be deemed to be outstanding,
         and (iii) all rights of the holders thereof as holders of Series D
         Preferred Units shall cease (except the rights to convert and to
         receive the cash payable upon such redemption, without interest
         thereon, upon surrender and endorsement of their certificates if so
         required and to receive any distributions payable thereon). The
         Partnership's obligation to provide cash in accordance with the
         preceding sentence shall be deemed fulfilled if, on or before the Call
         Date, the Partnership shall deposit with a bank or trust company (which
         maybe an affiliate of the Partnership) that has an office in the
         Borough of Manhattan, City of New York, and that has, or is an
         affiliate of a bank or trust company that has, capital and surplus of
         at least $50,000,000, necessary for such redemption, in trust, with
         irrevocable instructions that such cash be applied to the redemption of
         the Series D Preferred Units so called for redemption. No interest
         shall accrue for the benefit of the holders of Series D Preferred Units
         to be redeemed on any cash so set aside by the Partnership. Subject to
         applicable escheat laws, any such cash unclaimed at the end of two
         years from the Call Date shall revert to the general funds of the
         Partnership, after which reversion the holders of such shares so called
         for redemption shall look only to the general funds of the Partnership
         for the payment of such cash.

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                     As promptly as practicable after the Call Date, such Series
         D Preferred Units shall be exchanged for any cash (without interest
         thereon) for which such Series D Preferred Units have been redeemed,
         such exchange to be evidenced by appropriate amendments of Exhibit A to
         the Agreement and payment to the holder thereof (as shown on the
         records of the Partnership) of such cash. If fewer than all the
         outstanding Series D Preferred Units are to be redeemed, shares to be
         redeemed shall be selected by the Partnership from outstanding Series D
         Preferred Units not previously called for redemption pro rata (as
         nearly as may be), by lot or by any other method determined by the
         Partnership in its sole discretion to be equitable.

         Section 6.  CONVERSION. Holders of Series D Preferred Units shall have
the right to convert all or a portion of such units into Common Units, as
follows:

                     (a) Subject to and upon compliance with the provisions of
         this Section 6, a holder of Series D Preferred Units shall have the
         right, at his or her option, at any time after the earliest to occur of
         (i) the sixty first day after such holder provides the Partnership with
         written notice of its intent to convert Series D Preferred Units, (ii)
         the first day on which a Change of Control occurs, (iii) the occurrence
         of a REIT Termination Event, or (iv) such date as determined by the
         Partnership (the "Conversion Date"), to convert all or any portion of
         such units (or such units as determined by the General Partner if
         pursuant to clause (iv) above) into the number of Common Units obtained
         by dividing the aggregate Liquidation Preference of such units
         (inclusive of accrued but unpaid distributions) by the Conversion Price
         (as in effect at the time and on the date provided for in the last
         paragraph of paragraph (b) of this Section 6), such conversion to be
         made in the manner provided in paragraph (b) of this Section 6;
         PROVIDED, HOWEVER, that the right to convert units called for
         redemption pursuant to Section 5 shall terminate at the close of
         business on the fifth Business Day prior to the Call Date fixed for
         such redemption, unless the Partnership shall default in making payment
         of the cash payable upon such redemption under Section 5.

                     (b) In order to exercise the conversion right, the holder
         of each Series D Preferred Unit to be converted shall irrevocably
         instruct the General Partner in a writing duly executed by the holder
         or the holder's duly authorized attorney, with signature guaranteed, to
         convert such units into Common Units. The General Partner, in its sole
         discretion, may require such holder to provide additional instruments
         of transfer as its deems necessary or desirable to effect the
         conversion. Each instruction shall be accompanied by an amount
         sufficient to pay any transfer or similar tax (or evidence reasonably
         satisfactory to the General Partner demonstrating that such taxes have
         been paid).

                     Each conversion shall be deemed to have been effected
         immediately prior to the close of business on the date on which such
         instruction and such notice shall have been received by the General
         Partner as aforesaid (and if applicable, payment of an amount equal to
         the distribution payable on such units shall have been received by the
         General Partner as described above) and such conversion shall be at the
         Conversion Price in effect at such time on such date.

                     Holders of Series D Preferred Units at the close of
         business on a distribution payment record date shall be entitled to
         receive the distribution payable on such units on

                                       10
<PAGE>

         the corresponding Distribution Payment Date notwithstanding the
         conversion thereof following such distribution payment record date and
         prior to such Distribution Payment Date. However, the holder of Series
         D Preferred Units converted during the period between the close of
         business on any distribution payment record date and the opening of
         business on the corresponding Distribution Payment Date (except Series
         D Preferred Units converted after the issuance of notice of redemption
         with respect to a Call Date during such period, such Series D Preferred
         Units being entitled to such distribution on the Distribution Payment
         Date) must pay to the Partnership an amount equal to the distribution
         payable on such units on such Distribution Payment Date. A holder of
         Series D Preferred Units on a distribution payment record date who
         converts Series D Preferred Units into Common Units on the
         corresponding Distribution Payment Date will receive the distribution
         payable by the Partnership on such Series D Preferred Units on such
         date, and the converting holder need not pay the amount of such
         distribution upon conversion. Except as provided above, the Partnership
         shall make no payment or allowance for unpaid distributions, whether or
         not in arrears, on converted units or for distributions on the Common
         Units issued upon such conversion.

                     (c) In lieu of any fractional interest in a Common Unit
         that would otherwise be deliverable upon the conversion of a Series D
         Preferred Share, the General Partner, in its sole discretion, may cause
         the Partnership to pay to the holder of such fractional unit an amount
         in cash based upon the Fair Market Value of the Common Units on the
         Trading Day immediately preceding the date of conversion. If more than
         one unit shall be surrendered for conversion at one time by the same
         holder, the number of full Common Units issuable upon conversion
         thereof shall be computed on the basis of the aggregate number of
         Series D Preferred Units so surrendered.

                     (d) The Conversion Price shall be adjusted from time to
         time as follows:

                         (i)   If the Partnership shall after the Issue Date (A)
                     make a distribution on its Partnership Units in Common
                     Units, (B) subdivide its outstanding Common Units into a
                     greater number of units, (C) combine its outstanding Common
                     Units into a smaller number of units or (D) issue any
                     Partnership Units by reclassification of its Common Units,
                     the Conversion Price in effect at the opening of business
                     on the day following the date fixed for the determination
                     of unitholders entitled to receive such distribution or
                     distribution or at the opening of business on the Business
                     Day next following the day on which such subdivision,
                     combination or reclassification becomes effective, as the
                     case may be, shall be adjusted so that the holder of any
                     Series D Preferred Units thereafter surrendered for
                     conversion shall be entitled to receive the number of
                     Common Units that such holder would have owned or have been
                     entitled to receive after the happening of any of the
                     events described above as if such Series D Preferred Units
                     had been converted immediately prior to the record date in
                     the case of a distribution or distribution or the effective
                     date in the case of a subdivision, combination or
                     reclassification. An adjustment made pursuant to this
                     subparagraph (i) shall become effective immediately after
                     the opening of business on the Business Day next following
                     the record date (except as provided in paragraph (h) below)
                     in the case of a distribution and shall become effective
                     immediately after the opening of

                                       11
<PAGE>

                     business on the Business Day next following the effective
                     date in the case of a subdivision, combination or
                     reclassification.

                         (ii)  If the Partnership shall issue after the Issue
                     Date rights, options or warrants to all holders of Common
                     Units entitling them (for a period expiring within 45 days
                     after the record date mentioned below) to subscribe for or
                     purchase Common Units at a price per share less than 95%
                     (100% if a stand-by underwriter is used and charges the
                     Partnership a commission) of the Fair Market Value per
                     Common Unit on the record date for the determination of
                     unitholders entitled to receive such rights, options or
                     warrants, then the Conversion Price in effect at the
                     opening of business on the Business Day next following such
                     record date shall be adjusted to equal the price determined
                     by multiplying (A) the Conversion Price in effect
                     immediately prior to the opening of business on the
                     Business Day next following the date fixed for such
                     determination by (B) a fraction, the numerator of which
                     shall be the sum of (x) the number of Common Units
                     outstanding on the close of business on the date fixed for
                     such determination and (y) the number of shares that the
                     aggregate proceeds to the Partnership from the exercise of
                     such rights, options or warrants for Common Units would
                     purchase at 95% of such Fair Market Value (or 100% in the
                     case of a stand-by underwriting), and the denominator of
                     which shall be the sum of (x) the number of Common Units
                     outstanding on the close of business on the date fixed for
                     such determination and (y) the number of additional Common
                     Units offered for subscription or purchase pursuant to such
                     rights, options or warrants. Such adjustment shall become
                     effective immediately after the opening of business on the
                     day next following such record date (except as provided in
                     paragraph (h) below). In determining whether any rights,
                     options or warrants entitle the holders of Common Units to
                     subscribe for or purchase Common Units at less than 95% of
                     such Fair Market Value (or 100% in the case of a stand-by
                     underwriting), there shall be taken into account any
                     consideration received by the Partnership upon issuance and
                     upon exercise of such rights, options or warrants, the
                     value of such consideration, if other than cash, to be
                     determined by the General Partner whose determination shall
                     be conclusive.

                         (iii) If the Partnership shall distribute to all
                     holders of its Common Units any securities of the
                     Partnership (other than Common Units) or evidence of its
                     indebtedness or assets (excluding cumulative cash
                     distributions or distributions paid with respect to the
                     Common Units after December 31, 2000 which are not in
                     excess of the following: the sum of (A) the Partnership's
                     cumulative undistributed Funds from Operations at December
                     31, 2000, plus (B) the cumulative amount of Funds from
                     Operations, as determined by the General Partner, after
                     December 31, 2000, minus (C) the cumulative amount of
                     distributions accrued or paid in respect of the Series D
                     Preferred Units or any other class or series of preferred
                     units of the Partnership after the Issue Date or rights,
                     options or warrants to subscribe for or purchase any of its
                     securities (excluding those rights, options and warrants
                     issued to all holders of Common Units entitling them for a
                     period expiring within 45 days after the record date
                     referred to in subparagraph (ii) above to subscribe for or
                     purchase Common Units, which rights and warrants are
                     referred to in and treated

                                       12
<PAGE>

                     under subparagraph (ii) above) (any of the foregoing being
                     hereinafter in this subparagraph (iii) collectively called
                     the "SECURITIES" and individually a "SECURITY"), then in
                     each such case the Conversion Price shall be adjusted so
                     that it shall equal the price determined by multiplying (x)
                     the Conversion Price in effect immediately prior to the
                     close of business on the date fixed for the determination
                     of unitholders entitled to receive such distribution by (y)
                     a fraction, the numerator of which shall be the Fair Market
                     Value per Common Unit on the record date mentioned below
                     less the then fair market value (as determined by the
                     General Partner, whose determination shall be conclusive)
                     of the portion of the Securities or assets or evidences of
                     indebtedness so distributed or of such rights, options or
                     warrants applicable to one Common Unit, and the denominator
                     of which shall be the Fair Market Value per Common Unit on
                     the record date mentioned below. Such adjustment shall
                     become effective immediately at the opening of business on
                     the Business Day next following (except as provided in
                     paragraph (h) below) the record date for the determination
                     of unitholders entitled to receive such distribution. For
                     the purposes of this subparagraph (iii), the distribution
                     of a Security, which is distributed not only to the holders
                     of the Common Units on the date fixed for the determination
                     of unitholders entitled to such distribution of such
                     Security, but also is distributed with each Common Unit
                     delivered to a Person converting a Series D Preferred Unit
                     after such determination date, shall not require an
                     adjustment of the Conversion Price pursuant to this
                     subparagraph (iii); PROVIDED that on the date, if any, on
                     which a person converting a Series D Preferred Unit would
                     no longer be entitled to receive such Security with a
                     Common Unit (other than as a result of the termination of
                     all such Securities), a distribution of such Securities
                     shall be deemed to have occurred and the Conversion Price
                     shall be adjusted as provided in this subparagraph (iii)
                     (and such day shall be deemed to be tithe date fixed for
                     the determination of the unitholders entitled to receive
                     such distribution" and "the record date" within the meaning
                     of the two preceding sentences).

                         (iv)  In case a tender or exchange offer (which term
                     shall not include open market repurchases by the
                     Partnership) made by the Partnership or any subsidiary of
                     the Partnership for all or any portion of the Common Units
                     shall expire and such tender or exchange offer shall
                     involve the payment by the Partnership or such subsidiary
                     of consideration per Common Unit having a fair market value
                     (as determined in good faith by the General Partner, whose
                     determination shall be conclusive), at the last time (the
                     "EXPIRATION TIME") tenders or exchanges may be made
                     pursuant to such tender or exchange offer, that exceeds the
                     Current Market Price per Common Unit on the Trading Day
                     next succeeding the Expiration Time, the Conversion Price
                     shall be reduced so that the same shall equal the price
                     determined by multiplying the Conversion Price in effect
                     immediately prior to the effectiveness of the Conversion
                     Price reduction contemplated by this subparagraph, by a
                     fraction of which the numerator shall be the number of
                     Common Units outstanding (including any tendered or
                     exchanged units) at the Expiration Time, multiplied by the
                     Current Market Price per Common Unit on the Trading Day
                     next succeeding the Expiration Time, and the denominator
                     shall be the sum of (A) the fair market value (determined
                     as

                                       13
<PAGE>

                     aforesaid) of the aggregate consideration payable to
                     unitholders based upon the acceptance (up to any maximum
                     specified in the terms of the tender or exchange offer) of
                     all shares validly tendered or exchanged and not withdrawn
                     as of the Expiration Time (the shares deemed so accepted,
                     up to any maximum, being referred to as the "PURCHASED
                     UNITS") and (B) the product of the number of Common Units
                     outstanding (less any Purchased Units) at the Expiration
                     Time and the Current Market Price per Common Unit on the
                     Trading Day next succeeding the Expiration Time, such
                     reduction to become effective immediately prior to the
                     opening of business on the day following the Expiration
                     Time.

                         (v)   No adjustment in the Conversion Price shall be
                     required unless such adjustment would require a cumulative
                     increase or decrease of at least 1 % in such price;
                     PROVIDED, HOWEVER, that any adjustments that by reason of
                     this subparagraph (v) are not required to be made shall be
                     carried forward and taken into account in any subsequent
                     adjustment until made; and PROVIDED, FURTHER, that any
                     adjustment shall be required and made in accordance with
                     the provisions of this Section 6 (other than this
                     subparagraph (v)) not later than such time as may be
                     required in order to preserve the tax-free nature of a
                     distribution to the holders of Common Units:
                     Notwithstanding any other provisions of this Section 6, the
                     Partnership shall not be required to make any adjustment of
                     the Conversion Price for the issuance of any Common Units
                     pursuant to any plan providing for the reinvestment of
                     distributions or interest payable on securities of the
                     Partnership and the investment of additional optional
                     amounts in Common Units under such plan. All calculations
                     under this Section 6 shall be made to the nearest cent
                     (with $.005 being rounded upward) or to the nearest
                     one-tenth of a unit (with .05 of a unit being rounded
                     upward), as the case may be. Anything in this paragraph (d)
                     to the contrary notwithstanding, the Partnership shall be
                     entitled, to the extent permitted by law, to make such
                     reductions in the Conversion Price, in addition to those
                     required by this paragraph (d), as it in its discretion
                     shall determine to be advisable in order that any share
                     distributions, subdivision of shares, reclassification or
                     combination of shares, distribution of rights or warrants
                     to purchase shares or securities, or distribution of other
                     assets (other than cash distributions) hereafter made by
                     the Partnership to its partners shall not be taxable.

                     (e) If the Partnership shall be a party to any transaction
         (including without limitation a merger, consolidation, self tender
         offer for all or substantially all of its Common Units, sale of all or
         substantially all of the Partnership's assets or recapitalization of
         the Common Units and excluding any transaction as to which subparagraph
         (d)(i) of this Section 6 applies) (each of the foregoing being referred
         to herein as a "TRANSACTION"), in each case as a result of which all or
         substantially all of the Common Units are converted into the right to
         receive shares, securities or other property (including cash or any
         combination thereof), each Series D Preferred Unit which is not
         redeemed or converted into the right to receive shares, securities or
         other property prior to such Transaction shall thereafter be
         convertible into the kind and amount of shares, securities and other
         property (including cash or any combination thereof) receivable upon
         the consummation of such Transaction by a holder of that number of
         Common Units into

                                       14
<PAGE>

         which one Series D Preferred Unit was convertible immediately prior to
         such Transaction, assuming such holder of Common Units (i) is not a
         Person with which the Partnership consolidated or into which the
         Partnership merged or which merged into the Partnership or to which
         such sale or transfer was made, as the case may be ("CONSTITUENT
         PERSON"), or an affiliate of a Constituent Person and (ii) failed to
         exercise his rights of election, if any, as to the kind or amount of
         shares, securities and other property (including cash) receivable upon
         such Transaction (provided that if the kind or amount of shares,
         securities and other property (including cash) receivable upon such
         Transaction is not the same for each Common Unit held immediately prior
         to such Transaction by other than a Constituent Person or an affiliate
         thereof and in respect of which such rights of election shall not have
         been exercised ("NON-ELECTING UNIT"), then for the purpose of this
         paragraph (e) the kind and amount of shares, securities and other
         property (including cash) receivable upon such Transaction by each
         Non-Electing Unit shall be deemed to be the kind and amount so
         receivable per unit by holders of a plurality of the Non-Electing
         Units). The Partnership shall not be a party to any Transaction unless
         the terms of such Transaction are consistent with the provisions of
         this paragraph (e), and it shall not consent or agree to the occurrence
         of any Transaction until the Partnership has entered into an agreement
         with the successor or purchasing entity, as the case may be, for the
         benefit of the holders of the Series D Preferred Units that will
         contain provisions enabling the holders of the Series D Preferred Units
         that remain outstanding after such Transaction to convert into the
         consideration received by holders of Common Units at the Conversion
         Price in effect immediately prior to such Transaction. The provisions
         of this paragraph (e) shall similarly apply to successive Transactions.

                     (f) If:

                         (i)   the Partnership shall declare a distribution on
                     its Common Units (other than cash distributions or
                     distributions paid with respect to the Common Units after
                     December 31, 2000 not in excess of the sum of the
                     Partnership's cumulative undistributed Funds from
                     Operations at December 31, 2000, plus the cumulative amount
                     of Funds from Operations, as determined by the General
                     Partner, after December 31, 2000, minus the cumulative
                     amount of distributions accrued or paid in respect of the
                     Series D Preferred Units or any other class or series of
                     preferred units of the Partnership after the Issue Date);
                     or

                         (ii)  the Partnership shall authorize the granting to
                     all holders of Common Units of rights, options or warrants
                     to subscribe for or purchase any units of any class or any
                     other rights, options or warrants; or

                         (iii) there shall be any reclassification of the Common
                     Units (other than an event to which subparagraph (d)(i) of
                     this Section 6 applies) or any consolidation or merger to
                     which the Partnership is a party (other than a merger in
                     which the Partnership is the surviving entity) and for
                     which approval of any partners of the Partnership is
                     required, or a self tender offer by the Partnership for all
                     or substantially all of its outstanding Common Units or the
                     sale or transfer of all or substantially all of the assets
                     of the Partnership as an entirety; or

                                       15
<PAGE>

                         (iv)  there shall occur the voluntary or involuntary
                     liquidation, dissolution or winding up of the Partnership;

         then the General Partner shall cause to be mailed to the holders of
         Series D Preferred Units at their addresses as shown on the records of
         the Partnership, as promptly as possible, but at least 10 days prior to
         the applicable date hereinafter specified, a notice stating (A) the
         date on which a record is to be taken for the purpose of such
         distribution,-or granting of rights, options or warrants, or, if a
         record is not to be taken, the date as of which the holders of Common
         Units of record to be entitled to such distribution, or rights, options
         or warrants are to be determined or (B) the date on which such
         reclassification, consolidation, merger, sale, transfer, liquidation,
         dissolution or winding up is expected to become effective, and the date
         as of which it is expected that holders of Common Units of record shall
         be entitled to exchange their Common Units for securities or other
         property, if any, deliverable upon such reclassification,
         consolidation, merger, sale, transfer, liquidation, dissolution or
         winding up. Failure to give or receive such notice or any defect
         therein shall not affect the legality or validity of the proceedings
         described in this Section 6.

                     (g) Whenever the Conversion Price is adjusted as herein
         provided, the General Partner shall promptly (i) execute and file in
         its records an officer's certificate setting forth the Conversion Price
         after such adjustment and setting forth a brief statement of the facts
         requiring such adjustment which certificate shall be conclusive
         evidence of the correctness of such adjustment absent manifest error,
         and (ii) prepare a notice of such adjustment of the Conversion Price
         setting forth the adjusted Conversion Price and the effective date of
         such adjustment and shall mail such notice of such adjustment of the
         Conversion Price to the holder of each Series D Preferred Unit at such
         holder's last address as shown on the records of the Partnership.

                     (h) In any case in which paragraph (d) of this Section 6
         provides that an adjustment shall become effective on the day next
         following the record date for an event, the Partnership may defer until
         the occurrence of such event (A) issuing to the holder of any Series D
         Preferred Unit converted after such record date and before the
         occurrence of such event the additional Common Units issuable upon such
         conversion by reason of the adjustment required by such event over and
         above the Common Units issuable upon such conversion before giving
         effect to such adjustment and (B) paying to such holder any amount of
         cash in lieu of any fraction pursuant to paragraph (c) of this Section
         6.

                     (i) There shall be no adjustment of the Conversion Price in
         case of the issuance of any shares of beneficial interest of the
         Partnership in a reorganization, acquisition or other similar
         transaction except as specifically set forth in this Section 6. If any
         action or transaction would require adjustment of the Conversion Price
         pursuant to more than one paragraph of this Section 6, only one
         adjustment shall be made and such adjustment shall be the amount of
         adjustment that has the highest absolute value.

                     (j) If the Partnership shall take any action affecting the
         Common Units, other than action described in this Section 6, that in
         the opinion of the General Partner would materially and adversely
         affect the conversion rights of the holders of the Series D

                                       16
<PAGE>

         Preferred Units, the Conversion Price for the Series D Preferred Units
         may be adjusted, to the extent permitted by law, in such manner, if
         any, and at such time, as the General Partner, in its sole discretion,
         may determine to be equitable in the circumstances.

                         The Partnership shall endeavor to comply with all
         federal and state securities laws and regulations thereunder in
         connection with the issuance of any securities that the Partnership
         shall be obligated to deliver upon conversion of the Series D Preferred
         Units.

                     (k) The Partnership will pay any and all documentary stamp
         or similar issue or transfer taxes payable in respect of the issue or
         delivery of Common Units or other securities or property on conversion
         of the Series D Preferred Units pursuant hereto; provided, however,
         that the Partnership shall not be required to pay any tax that may be
         payable in respect of any transfer involved in the issue or delivery of
         Common Units or other securities or property in a name other than that
         of the holder of the Series D Preferred Units to be converted, and no
         such issue or delivery shall be made unless and until the person
         requesting such issue or delivery has paid to the Partnership the
         amount of any such tax or established, to the reasonable satisfaction
         of the Partnership, that such tax has been paid.

         Section 7.  RANKING. Any class or series of Partnership Units shall be
deemed to rank:

                     (a) prior to the Series D Preferred Units, as to the
         payment of distributions and as to distribution of assets upon
         liquidation, dissolution or winding up, if the holders of such class or
         series shall be entitled to the receipt of distributions or of amounts
         distributable upon liquidation, dissolution or winding up, as the case
         may be, in preference or priority to the holders of Series D Preferred
         Units;

                     (b) on a parity with the Series D Preferred Units, as to
         the payment of distributions and as to distribution of assets upon
         liquidation, dissolution or winding up, whether or not the distribution
         rates, Distribution Payment Dates or redemption or liquidation prices
         per share thereof shall be different from those of the Series D
         Preferred Units, if the holders of such class or series and the Series
         D Preferred Units shall be entitled to the receipt of distributions and
         of amounts distributable upon liquidation, dissolution or winding up in
         proportion to their respective amounts of accrued and unpaid
         distributions per share or liquidation preferences, without preference
         or priority one over the other ("PARITY PREFERRED UNITS");

                     (c) junior to the Series D Preferred Units, as to the
         payment of distributions or as to the distribution of assets upon
         liquidation, dissolution or winding up, if such class or series shall
         be Junior Shares; and

                     (d) junior to the Series D Preferred Units, as to the
         payment of distributions and as to the distribution of assets upon
         liquidation, dissolution or winding up, if such class or series shall
         be Fully Junior Units.

         Section 8.  VOTING. Except as expressly provided herein, the holders of
Series D Preferred Units shall have no voting rights.

                                       17
<PAGE>

         So long as any Series D Preferred Units are outstanding, in addition to
any other vote or consent of partners required by law or by the Partnership
Agreement, the affirmative vote of at least 51 % of the votes entitled to be
cast by the holders of the Series D Preferred Units given in person or by proxy,
either in writing without a meeting or by vote at any meeting called for the
purpose, shall be necessary for effecting or validating:

                     (a) Any amendment, alteration or repeal of any of the
         provisions of the Agreement that materially and adversely affects the
         voting powers, rights or preferences of the holders of the Series D
         Preferred Units; PROVIDED, HOWEVER, that the amendment of the
         provisions of the Partnership Agreement so as to authorize or create or
         to increase the authorized amount of, any Parity Preferred Units, Fully
         Junior Units or Junior Units that are not senior in any respect to the
         Series D Preferred Units shall not be deemed to materially adversely
         affect the voting powers, rights or preferences of the holders of
         Series D Preferred Units; or

                     (b) A consolidation with or merger of the Partnership into
         another entity, or a consolidation with or merger of another entity
         into the Partnership, unless in each such case each Series D Preferred
         Units (i) shall remain outstanding without a material and adverse
         change to its terms and rights or (ii) shall be converted into or
         exchanged for convertible securities of the surviving entity having
         preferences, conversion or other rights, voting powers, restrictions,
         limitations as to distributions, qualifications and terms or conditions
         of redemption thereof identical to that of a Series D Preferred Unit
         (except for changes that do not materially and adversely affect the
         holders of the Series D Preferred Units);

PROVIDED, HOWEVER, that no such vote of the holders of Series D Preferred Units
shall be required if, at or prior to the time when such amendment, alteration or
repeal is to take effect, or when the issuance of any such prior shares or
convertible security is to be made, as the case may be, provision is made for
the redemption of all Series D Preferred Units at the time outstanding to the
extent such redemption is authorized by Section 5 hereof.

         For purposes of the foregoing provisions of this Section 8, each Series
D Preferred Unit shall have one (1) vote per unit, except that when any other
series of Preferred Units shall have the right to vote with the Series D
Preferred Units as a single class on any matter, then the Series D Preferred
Units and such other series shall have with respect to such matters one (1) vote
per $26.50 (or less pursuant to Section 4(a) hereof) of stated liquidation
preference. Except as otherwise required by applicable law or as set forth
herein, the Series D Preferred Units shall not have any relative, participating,
optional or other special voting rights and powers other than as set forth
herein, and the consent of the holders thereof shall not be required for the
taking of any Partnership action.

         Section 9.  RECORD HOLDERS. The General Partner may deem and treat the
record holder of any Series D Preferred Units as the true and lawful owner
thereof for all purposes, and the General Partner shall not be affected by any
notice to the contrary.

         III. AMENDMENT TO SECTION 5.01. Section 5.01 is amended by amending and
restating in its entirety Section 5.01(a) as follows:

                                       18
<PAGE>

         (a) GENERAL.

         (1) PROFIT.

         (A) First, 100% to the General partner and Common Unitholders until the
aggregate amount of Profit allocated under this SECTION 5.01(a)(1)(A) shall
equal the aggregate amount of Loss allocated to the Partners under SECTION
5.01(a)(2)(E);

         (B) Second, 100% to each Series B Preferred Unitholder, Series C
Preferred Unitholder and Series D Preferred Unitholder in proportion to and to
the extent of their respective excesses of (i) the aggregate amount of Loss
allocated to each under SECTION 5.01(a)(2)(D) over (ii) the aggregate amount of
Profit allocated to each under this SECTION 5.01(a)(1)(B);

         (C) Third, 100% to the General Partner and the Common Unitholders in
proportion to and to the extent of their respective excesses of (i) the
aggregate amount of Loss allocated to each under SECTION 5.01(a)(2)(C) over (ii)
the aggregate amount of Profit allocated to each under this SECTION
5.01(a)(1)(C);

         (D) Fourth, 100% proportionately to (i) each Series B Preferred
Unitholder until the aggregate amount of Profit allocated to each Series B
Preferred Unitholder under this SECTION 5.01(a)(1)(D)(i) shall equal the Series
B Preferred Distribution Amount, (ii) each Series C Preferred Unitholder until
the aggregate amount of Profit allocated to each Series C Preferred Unitholder
under this SECTION 5.01(a)(1)(D)(ii) shall equal the Series C Preferred
Distribution Amount and (iii) each Series D Preferred Unitholder until the
aggregate amount of Profit allocated to each Series D Preferred Unitholder under
this SECTION 5.01(a)(1)(D)(iii) shall equal the Series D Preferred Distribution
Amount; and

         (E) Fifth, 100% to the General Partner and the Common Unitholders in
accordance with the Percentage Interest of each.

         (2) LOSS.

         (A) First, 100% to the General Partner and the Common Unitholders to
the extent of and in proportion to (i) the aggregate amount of Profit allocated
to each under SECTION 5.01(a)(1)(E) over (ii) the aggregate amount of Loss
allocated to each under this SECTION 5.01(a)(2)(A);

         (B) Second, 100% proportionately to (i) each Series B Preferred
Unitholder to the extent of the Undistributed Series B Preferred Unit
Distribution Amount, (ii) each Series C Preferred Unitholder to the extent of
the Undistributed Series C Preferred Unit Distribution Amount and (iii) each
Series D Preferred Unitholder to the extent of the Undistributed Series D
Preferred Unit Distribution Amount;

         (C) Third, 100% to the General Partner and the Common Unitholders in
proportion to the Percentage Interest of each until the Capital Account balances
of both the General Partner and each Common Unitholder shall equal zero;

                                       19
<PAGE>

         (D) Fourth, 100% to each Series B Preferred Unitholder, Series C
Preferred Unitholder and Series D Preferred Unitholder in proportion to the
Capital Account balances of each until the Capital Account balance of each
Series B Preferred Unitholder, Series C Preferred Unitholder and Series D
Preferred Unitholder shall equal zero; and

         (E) Fifth, 100% to the General Partner and Common Unitholders in
accordance with their Percentage Interests.

         (3) DEFINITIONS. For purposes of this Section 5.01(a), the following
terms shall have the meanings indicated:

             "COMMON UNITHOLDER(S)" means all Persons holding a Limited
         Partnership Interest in the Partnership other than the Series B
         Preferred Unitholders, Series C Preferred Unitholders and Series D
         Preferred Unitholders.

             "SERIES B PREFERRED UNIT DISTRIBUTION AMOUNT" means the amount
         distributable to the Series B Preferred Unitholders as provided in
         Section 4.02(e) of the Second Amendment to the Second Amended and
         Restated Agreement of Limited Partnership of the Partnership dated June
         25, 1998.

             "SERIES B PREFERRED UNITHOLDER" means any Person holding Series B
         Preferred Units.

             "SERIES B PREFERRED UNITS" means the Series B Cumulative Redeemable
         Perpetual Preferred Units of Partnership Interest issued pursuant to
         the Second Amendment to the Second Amended and Restated Agreement of
         Limited Partnership of the Partnership dated June 25, 1998.

             "SERIES C PREFERRED UNIT DISTRIBUTION AMOUNT" means the amount
         distributable to the Series C Preferred Unitholders as provided in
         Section 4.02(f) of the Eighth Amendment to the Second Amended and
         Restated Agreement of Limited Partnership of the Partnership dated
         September 17, 1999.

             "SERIES C PREFERRED UNITHOLDER" means any Person holding Series C
         Preferred Units.

             "SERIES C PREFERRED UNITS" means the Series C Cumulative Redeemable
         Perpetual Preferred Units of Partnership Interest issued pursuant to
         the Eighth Amendment to the Second Amended and Restated Agreement of
         Limited Partnership of the Partnership dated September 17, 1999.

             "SERIES D PREFERRED UNIT DISTRIBUTION AMOUNT" means the amount
         distributable to the Series D Preferred Unitholders as provided in
         Section 4.02(g) of this Thirteenth Amendment.

             "SERIES D PREFERRED UNITHOLDER" means any Person holding Series D
         Preferred Units.

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<PAGE>

             "SERIES D PREFERRED UNITS" means the Series D Cumulative
         Convertible Redeemable Preferred Units of Partnership Interest issued
         pursuant to this Thirteenth Amendment.

             "UNDISTRIBUTED SERIES B PREFERRED UNIT DISTRIBUTION AMOUNT" means
         the excess of (i) the aggregate amount of Profit allocated to the
         Series B Unitholders under SECTION 5.01(a)(1)(D) and (ii) the
         aggregated amount of distributions made to the Series B Unitholders
         under Section 3 of Section 4.02(e) of the Second Amendment to the
         Second Amended and Restated Agreement of Limited Partnership of the
         Partnership dated June 25, 1998.

             "UNDISTRIBUTED SERIES C PREFERRED UNIT DISTRIBUTION AMOUNT" means
         the excess of (i) the aggregate amount of Profit allocated to the
         Series C Unitholders under SECTION 5.01(a)(1)(D) and (ii) the
         aggregated amount of distributions made to the Series C Unitholders
         under Section 3 of Section 4.02(f) of the Eighth Amendment to the
         Second Amended and Restated Agreement of Limited Partnership of the
         Partnership dated September 17, 1999.

             "UNDISTRIBUTED SERIES D PREFERRED UNIT DISTRIBUTION AMOUNT" means
         the excess of (i) the aggregate amount of Profit allocated to the
         Series D Unitholders under SECTION 5.01(a)(1)(D) and (ii) the
         aggregated amount of distributions made to the Series D Unitholders
         under Section 3 of Section 4.02(g) of this Thirteenth Amendment.

         IV. AMENDMENT TO EXHIBIT A. Exhibit A to the Agreement is hereby
amended and restated in its entirety as set forth on EXHIBIT A attached hereto.

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<PAGE>

         IN WITNESS WHEREOF, the General Partner has caused this Amendment to be
duly executed by its Senior Vice President this 20th day of March, 2001.

                                          PRENTISS PROPERTIES I, INC.



                                          By:  /s/ MICHAEL A. ERNST
                                              -------------------------------
                                          Name:    Michael A. Ernst
                                          Title:   Chief Financial Officer



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