EXHIBIT 10.13



                             FOURTH AMENDMENT TO THE
                            PRENTISS PROPERTIES TRUST
                            1996 SHARE INCENTIVE PLAN


         This Fourth Amendment to the Prentiss Properties Trust 1996 Share
Incentive Plan (the "Plan") as previously amended by the First through the Third
Amendments to the Plan, hereby amends the Plan effective as of October 15, 1996
in the following respects:

         1.       Section 8.02 of the Plan is hereby amended by the addition at
the end thereof of the following language:

         Attestation to the ownership of Shares or the assignment thereof to pay
         the exercise price and taxes shall be at the sole discretion of the
         Company. The Participant shall have no right to require the Company to
         accept payment in the form of shares. The Company may reject the
         attestation or assignment for any reason or no reason.

         The form of the attestation or assignment shall be on a form acceptable
         to the Company in any and all respects.

         Attestation to the ownership of Shares and the assignment thereof may
         be treated as the surrender of Shares under rules and procedures
         established by the Administrator. Any Shares surrendered, or attested
         to, must have been held by the surrendering Participant for more than
         six months, (or for any period required by the Company) and neither the
         surrender, or attestation to the ownership, of Shares shall be
         permitted if such action would cause the Company to recognize
         compensation expense (or additional compensation expense) with respect
         to the Option for financial reporting purposes.

         Any attempt to surrender shares, or any shares surrendered, or attested
         to, for any purpose, including payment of the Exercise Price and or
         taxes will be void AB INITIO, if such action would cause the Company to
         recognize compensation expense (or additional compensation expense)
         with respect to the Option for financial reporting purposes.

         Attestation to the ownership of Shares or the assignment thereof, may
         be only for the minimum number of Shares required to pay the exercise
         price and the minimum statutory taxes. Amounts in excess will be void
         AB INITIO

         2.       As amended by the foregoing, the Plan shall remain in full
force and effect.

Dated: May 9, 2001

                                  PRENTISS PROPERTIES TRUST



                                  By:  /s/ Thomas F. August
                                       -----------------------------------------
                                       Thomas F. August
                                       President and Chief Executive Officer