Purpose. MDM2 is an oncogene whose protein product may promote tumorigenesis by blocking wild-type p53 tumor suppressor mediated G0/G1 cell cycle arrest, thereby inhibiting repair of damaged DNA prior to cell division. While MDM2 DNA amplification is frequently observed in human sarcoma, the mechanisms linking this amplification to MDM2 oncoprotein over-production as well as its functional significance have not been well characterized in patients with soft tissue sarcoma.