Hydrogen peroxide yields in air-saturated methanol-water mixtures with methanol: water volume ratios varying from 199 to 1000, produced by60Co gamma-irradiation boith at room temperature and at 77 K have been determined. At room temperature, G(H2O2) values are almost constant over the entire range of methanol: water ratios. However, for irradiations at 77 K, G(H2O2) values increase with increasing methanol concentration up to the volume ratio of 982.