The irradiation is usually employed in sterilizing and crosslinking method of ultra-high molecular weight polyethylene (UHMWPE) bearing parts in orthopedic implants. The free radicals were formed in UHMWPE during this process in addition to crosslinking. The formed free radicals cause oxidative degradation of PE molecules by the reaction with oxygen during shelf storage and implantation in a long period. Electron spin resonance spectroscopic study was undertaken to investigate the remaining free radicals in UHMWPE after electron beam (EB) irradiation up to 500 kGy in N₂ environment. The heat treatment was employed at 110 ℃ and 145 ℃ for varying period of time to scavenge the free radicals. The free radicals were rapidly decayed for one hour and gradually decayed as a function of time by heat traement. The scavenging of free radicals was done more rapidly at 145 ℃ heat treatment than 110 ℃. Therefore longer heat treatment was required to scavenge all the free radicals formed in UHMWPE at 110 ℃. The oxidation profiles showed that the oxidation index (OI) of the heat-treated UHMWPE was lower than the OI of non heat-treated UHMWPE. The heat treatment of irradiated UHMWPE can substanially reduced the concentration of free radicals; thereby the UHMWPE has resistance against long-term oxidative degradation.