The radiation chemistry of poly(methacrylonitrile), which was gamma-irradiated at different temperatures (-196 degrees C, room temperature, 60 degrees C, 100 degrees C and 130 degrees C) and with different radiation doses, has been studied by electron spin resonance (e.s.r.) spectroscopy. When gamma-irradiated at -196 degrees C, radical anions and neutral radicals were formed. Warming the sample from -53 to -3 degrees C resulted in the conversion of the imide radical to the scission radical. The radical anions were found to decay in the temperature range from -196 to -100 degrees C. On annealing the sample to 23 degrees C, an e.s.r. spectrum similar to that obtained on gamma-irradiation at room temperature was obtained. The G(R .) values have been determined to be 2.2 on gamma-irradiation at -196 degrees C and 2.8 at room temperature. From photobleaching, microwave power saturation and annealing experiments, the major radical intermediates and their reactivities have been identified.