SUPPLEMENT TO PROSPECTUS DATED DECEMBER 14, 1999, AMENDED APRIL 5, 2000 24,550 SHARES OF KEYSTONE PROPERTY TRUST COMMON STOCK $0.001 PAR VALUE REGISTRATION NO. 333-92741 On March 7, 2003, an aggregate of 24,550 OP Units were transferred by means of gift from Michael G. Browning to Cathedral High School (the "Donee"). Subsequently, all of the OP Units were converted by the Donee into Common Shares on a 1:1 basis. The above-referenced Prospectus is hereby supplemented to update the table of selling security holders as follows: SHARES OWNED SHARES OWNED BEFORE OFFERING AFTER OFFERING ----------------------- REGISTERED -------------------- NAME NUMBER PERCENTAGE SHARES NUMBER PERCENTAGE ---- -------- ---------- ---------- ------ ---------- Michael G. Browning 443,117(3) 2.98%(3) 388,617 54,500 * Cathedral High School 24,550 * 24,550 0 -- ---------- The date of this Prospectus Supplement is March 18, 2003