The effects on methyl vinyl polysilicone foam of Co-60 gamma-ray radiation at room temperature was studied in air, in vacuo, and in an inert gas atmosphere. The unirradiated and irradiated samples were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, pyrolysis gas chromatography/mass spectroscopy, and thermogravimetric analysis, and the gas products after radiation were analyzed by gas chromatography/mass spectroscopy. The changes of the gel fraction, compression properties, and the stress-relaxation ratio with dose for irradiated samples were observed. The results show that the second crosslinking reaction in the polysilicone after chemical crosslinking took place at a low dose (2 X 10(5) Gy), but radiation degradation was predominant, with the dose increasing step by step. The mechanical properties of polysilicone foam gradually became low grade after it was irradiated by any dose in excess of 2 X 10(5) Gy. (C) 2003 Wiley Periodicals, Inc.