The properties of radicals from γ-ray irradiated silk fabrics were studiedby electron spin resonance method (ESR). The ESR spectra of silk fabrics irradiated inN2 showed a doublet at room temperature. The doublet became a singlet at g=2.0057after placing the sample in air for 24 hours. This can be explained by formation ofperoxide radicals. The radical concentration of the irradiated silk fabric and the decayrate of radicals are significantly affected by irradiation conditions, which include theabsorbed dose, atmosphere, and water content of the silk fabric samples. However, nodose rate effect on the radical concentration was observed. The results are of help in ourpractice of property modification of silk products by radiation graft copolymerization.``