The effects of methyl borate, iodine and potassium iodide on the Co-60 gamma radiolysis of methanol have been reinvestigated at room temperature, utilizing an experimental technique based on gas chromatographic determinations of the gaseous products of the radiolysis. The presence of methyl borate reduces the yield for ethylene glycol to some extent, with slight reductions of the yields for hydrogen and formaldehyde. The presence of iodine causes appreciable reduction of the yields for hydrogen, formaldehyde and ethylene glycol, with a slight reduction of the yield for methane. The presence of potassium iodide reduces the yields for hydrogen and ethylene glycol but increases that for formaldehyde. A mechanism of the radiolysis reaction is discussed, on the basis of the observed data.