The gamma-ray induced oxidation of ferrous sulfate in the presence of cupric sulfate was investigated. Radiation yields of this reaction are dependent on Fe++ ion, H+, Cu++ ion and dissolved O2 concentrations. The Cu++ ion is a very efficient inhibitor of Fe++ ion oxidation induced by free H and OH radicals in either the presence or absence of O2. At a pH of 2.0 the net oxidation of Fe++ ion is due solely to H2O2 formed in the gamma-ray "hot spot" or "spur." Molecular O2 is a product of the irradiation of air-free ferrous sulfate-cupric sulfate solutions. It is concluded that O2 originates by the reactions: OH + H2O, = HO2 + H2O followed by Cu++ + HO2 = Cu+ + H+ + O2. H2O2 ana OH radicals are postulated to react before appreciable diffusion of these products from their site of formation along the particle track takes place. The kinetics of the reactions are briefly discussed.