Freeze-dried preparations of actomyosin from chicken breast muscle were irradiated in liquid nitrogen with gamma radiation from a ce-sium-137 source at 5, 10, 15, 20, 30, 40, and 50 kGy. The ESR spectra at – 130°C were recorded with an EPR spectrometer. Signal intensities increased linearly with radiation. Analysis of data indicated a ten-fold rise in dose resulted in an almost seven-fold increase in number of free radicals generated. Determining the extent of such interaction on a major structural protein can help assess type and extent of reactions which might occur on irradiation of animal products.