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                                                                    EXHIBIT 10.9


                                 July 30, 1998



Developers Diversified Realty Corporation
34555 Chagrin Boulevard
Moreland Hills, Ohio

         Re:     Voting Agreement

Ladies and Gentlemen:

                 The undersigned understands that Developers Diversified Realty
Corporation, an Ohio corporation ("DDRC"), and American Industrial Properties
REIT, a Texas real estate investment trust ("AIP"), are entering into a Share
Purchase Agreement to be dated on or about the date hereof (the "Purchase
Agreement"), and, together with DDR Office Flex Corporation, a Delaware
corporation, a Merger Agreement to be dated on or about the date hereof (the
"Merger Agreement" and, together with the Purchase Agreement, the
"Agreements"), providing for, among other things, the purchase of common
shares, $.10 par value per share, of AIP by DDRC (the "Share Purchase").  Under
the rules of the New York Stock Exchange, consummation of the Share Purchase
will require the approval of the shareholders of AIP.

                 The undersigned is a shareholder of AIP (the "Shareholder")
and is entering into this letter agreement at your request, in exchange for
good and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, to induce you to enter into the Agreements and to consummate the
transactions contemplated thereby.

                 The Shareholder confirms its agreement with you as follows:

                 1.       The Shareholder represents and warrants that is the 
                          beneficial owner of the shares of beneficial interest
                          AIP listed on Schedule I annexed hereto (the "Shares")
                          of which the Shareholder or any affiliate (as defined
                          under the Securities Exchange Act of 1934, as amended)
                          of the Shareholder controlled by the Shareholder (a
                          "Controlled Affiliate") that has the power to vote or
                          to make recommendations regarding voting, and that the
                          Shareholder and the Controlled Affiliates, or the
                          clients on whose behalf the Shareholder or any
                          Controlled Person acts as a fiduciary, are, to the
                          best of the Shareholder's knowledge, on the date
                          hereof the lawful owners of the number of Shares set
                          forth in Schedule I, free and clear of all liens,
                          charges, encumbrances, voting agreements and
                          commitments of any kind, except as disclosed in
                          Schedule I.  Except for the Shares set forth in
                          Schedule I, neither the Shareholder nor any Controlled
                          Affiliate owns or holds any rights to acquire any
                          additional shares of beneficial interest of 


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Developers Diversified Realty Corporation
July 30, 1998
Page 2

                          AIP (other than pursuant to options or conversion
                          rights with regard to any of the Shares, in each case
                          as disclosed in Schedule I) or any interest therein
                          or any voting rights with respect to any such
                          additional shares.


                 2.       Until the earliest date referred to in 12, the 
                          Shareholder agrees that it will not, and will not
                          permit any Controlled Affiliate to, contract to sell,
                          sell or otherwise transfer or dispose of any of the
                          Shares or any interest therein or securities
                          convertible into shares of beneficial interest of AIP,
                          or any voting rights with respect thereto, without
                          your prior written consent.

                 3.       The Shareholder agrees that, during the term of this 
                          letter agreement, neither it nor any Controlled
                          Affiliate will take any action that AIP would be
                          prohibited from taking under Section 5.4 of the
                          Purchase Agreement.

                 4.       The Shareholder agrees that during the term of this 
                          letter agreement (a) all of the shares of beneficial
                          interest of AIP beneficially owned by the Shareholder
                          or any Controlled Affiliate, or over which the
                          Shareholder or any Controlled Affiliate has voting
                          power or control, directly or indirectly, including
                          any such shares acquired after the date hereof at the
                          record date for any meeting of shareholders of AIP
                          called to consider and vote on the Share Purchase and
                          the Agreements and the transactions contemplated
                          thereby or any Competing Transaction (as such term is
                          defined in the Purchase Agreement) will be voted by
                          the Shareholder or such Controlled Affiliates, or any
                          representative or proxy thereof, or that the
                          Shareholders will recommend that such Shares be voted,
                          as applicable, in favor of the approval of the Share
                          Purchase and the Agreements and the transactions
                          contemplated thereby and (b) neither the Shareholder
                          nor any Controlled Affiliate, nor any such
                          representative or proxy will vote any such Shares or
                          recommend that such Shares be voted, in favor of any
                          Competing Transaction, in each case except to the
                          extent that the Shareholder determines in its good
                          faith judgment, after consultation with its legal
                          counsel, that it is prudent to vote or recommend
                          otherwise in the exercise of its fiduciary
                          obligations.

                 5.       The Shareholder agrees that the shares referred to in 
                          Section 4 above, owned at the record date for any
                          meeting of shareholders of AIP called to consider and
                          vote on the election of members of the Board of Trust
                          Managers of the Trust (the "Board"), will be voted by
                          the Shareholder or any Controlled Affiliate, or any
                          representative or proxy
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Developers Diversified Realty Corporation
July 30, 1998
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                          thereof, or that the Shareholder will recommend that
                          such Shares be voted, as applicable, in favor of the
                          approval of the election of the representatives of
                          DDRC to the Board for so long as DDRC has the right
                          to nominate members of the Board under the Purchase
                          Agreement, in each case except to the extent that the
                          Shareholder determines in its good faith judgment,
                          after consultation with its legal counsel, that it is
                          prudent to vote or recommend otherwise in the
                          exercise of its fiduciary obligations.

                 6.       The Shareholder hereby appoints Marc A. Simpson to 
                          attend the special meeting of the shareholders of AIP
                          held to consider and vote on the Share Purchase and to
                          vote the shares referred to in Section 4 above, with
                          all the power the Shareholder would possess if
                          personally present, in favor of the approval of the
                          Share Purchase, the Agreements and the transactions
                          contemplated thereby.  The Shareholder agrees to
                          execute, and to cause each Controlled Affiliate to
                          execute, such proxies and other instruments, and to
                          take and to cause each Controlled Affiliate to take
                          such actions, as may be necessary to cause all of
                          those shares to be so voted.

                 7.       The Shareholder has all necessary power and authority 
                          to enter into this letter agreement.  This letter
                          agreement is the legal, valid and binding agreement of
                          the Shareholder, and is enforceable against the
                          Shareholder in accordance with its terms, subject to
                          applicable bankruptcy, insolvency, fraudulent
                          conveyance, reorganization, moratorium and similar
                          laws affecting creditors' rights and remedies
                          generally and to general principles of equity.  This
                          letter agreement shall inure to the benefit of the
                          parties hereto and the successors and assigns of DDRC.

                 8.       The Shareholder agrees that damages are an inadequate 
                          remedy for the breach by Shareholder of any term or
                          condition of this letter agreement and that you shall
                          be entitled to a temporary restraining order and
                          preliminary and permanent injunctive relief in order
                          to enforce our agreements herein.

                 9.       Except to the extent that the laws of the jurisdiction
                          of organization of any party hereto, or any other
                          jurisdiction, are mandatorily applicable to matters
                          arising under or in connection with this letter
                          agreement, this letter agreement shall be governed by
                          the laws of the State of Ohio.  All actions and
                          proceedings arising out of or relating to this letter
                          agreement shall be heard and determined in any United
                          States District Court sitting in the Northern District
                          of Ohio.
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Developers Diversified Realty Corporation
July 30, 1998
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                 10.      Each of the parties hereto irrevocably submits to the
                          exclusive jurisdiction of any United States District
                          Court located in the Northern District of Ohio, for
                          the purpose of any action or proceeding arising out of
                          or relating to this letter agreement and each of the
                          parties hereto irrevocably agrees that all claims in
                          respect of such action or proceeding may be heard and
                          determined exclusively in any federal court sitting in
                          the Northern District of Ohio.  Each of the parties
                          hereto agrees that a final judgment in any action or
                          proceeding shall be conclusive and may be enforced in
                          other jurisdictions by suit on the judgment or in any
                          other manner provided by law.

                 Shareholder hereby irrevocably appoints A.G.C. Co., 1900 East
9th Street, Suite 3200, Cleveland, Ohio, as its lawful agent in and for the
State of Ohio, for and in its behalf, to accept and acknowledge service of, and
upon whom may be served, all necessary processes in any action, suit, or
proceeding arising under this Agreement that may be had or brought against it
in any federal court in the Northern District of Ohio, such service of process
or notice, or the acceptance thereof by said agent endorsed thereon, to have
the same force and effect as if served upon such corporation or individual.
Nothing in this Section 10 shall affect the right of any party hereto to serve
legal process in any other manner permitted by law.  Shareholder hereby waives
all defenses of improper venue and forum non conveniens with respect to any
action, suit, or proceeding brought in the any United States District Court
located in the Northern District of Ohio and arising under this letter
agreement.

                 11.      This letter agreement constitutes the entire agreement
                          between the parties hereto with respect to the matters
                          covered hereby and supersedes all prior agreements,
                          understandings or representations between the parties,
                          written or oral, with respect to the subject matter
                          hereof.

                 12.      This letter agreement and the proxy granted pursuant
                          to Section 6 hereof shall become effective upon the
                          execution and delivery of the Agreements by the
                          respective parties thereto.  Except as otherwise
                          provided herein, this letter agreement and the proxy
                          granted pursuant to Section 6 hereof shall terminate
                          automatically, without the need for any notice or
                          other action by either party upon the earliest of (i)
                          the date on which the Purchase Agreement and the
                          Merger Agreement are terminated, (ii) the Second
                          Closing Date, as defined in the Purchase Agreement,
                          and (iii) the date that is 240 days after the date
                          hereof.

                 13.      Each of the parties hereto intends that AIP shall be a
                          third party beneficiary of this letter agreement, and
                          shall be entitled to the benefits hereof and shall
                          have the ability to exercise the rights granted to
                          DDRC herein as fully as if it were a signatory of this
                          letter agreement.
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Developers Diversified Realty Corporation
July 30, 1998
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                 14.      Notwithstanding anything to the contrary contained
                          herein, neither AIP nor any representative of the
                          Shareholder serving on the Board of Trust Managers of
                          AIP shall be deemed to be a Controlled Affiliate.

                 Please confirm that the foregoing correctly states the
understanding between us by signing and returning to me a counterpart hereof.

                                  LaSalle Advisors Limited Partnership
                                  
                                  
                                  By: /s/ [Illegible]
                                     -----------------------------------------
                                  Name: Illegible
                                       ---------------------------------------
                                  Title:   Illegible
                                        --------------------------------------
                                  
                                  ABKB/LaSalle Securities Limited Partnership
                                  
                                  By: /s/ [Illegible]
                                     -----------------------------------------
                                  Name: [Illegible]
                                       ---------------------------------------
                                  Title: [Illegible]
                                        --------------------------------------


Confirmed on the date
first above written

Developers Diversified Realty Corporation


By: /s/ Scott A. Wolstein 
   ----------------------------------------
Name: Scott A. Wolstein 
     --------------------------------------
Title: President 
      -------------------------------------
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                                   Schedule I

                   Ownership of Shares of Beneficial Interest


Owned Beneficially (including Options to Purchase Shares)

<TABLE>
<CAPTION>
                                                                        Total Number of Shares
                                                                         Beneficiallly Owned
                                                                         -------------------

 <S>                                                                           <C>
 LaSalle Securities                                                            960,425

 LaSalle Advisors                                                              542,153
</TABLE>