Ethylene-octene copolymer(POE)samples exposed to radiation under a series of doses were investigated using electron spin resonance spectroscopy(ESR). The mobility of the free radicals wasrestricted inthe crystalline phase. The captive free radical was observed in radiation POE from 273 K to 373 K and the intensity of free radicals showed the strongest signal around the melt temperature. However, the temperature dependence of the ESR signal intensity was interesting and needs further investigation.Cited