In an attempt to observe the possible radioprotective actions of single or combined application of reducedglutathione(GSH) and cold exposure in mammales, the albino mouse was subjected to GSH injection, cold exposure at-1+0.2C and whole-body X-irradiation with 900R either singularly or in comination, or the X-irradiation followingthe cold exposure and/or GSH injection. The level of protein of the liver, brain and heart was measured at onehour after each application, and the results were compared with the control, i.e., non-irradiated and non-coldexposed normal animal. Protein was measured by the method described byr Lowry et al., using Folin-Ciocalteauphenol reagent. The results thus obtained are summarized as follow: 1) the level of protein in the liver, brainand heart of the normal mouse was 101.13, 62.75 and 87.08 mg/gm wet wt., respectively. 2) The protein levels ofall the organs studied were elevated by the X-irradiation, but decreased protein levels were observed when GSH wasgiven. 3) In the group where the cold exposure was applied, and the X-irradiation was combined with the coldexposure, the protein levels of the organs were similar to the normal value or slightly decreased. 4) When GSH,X-irradiation and cold-exposure were combined, the protein levels of all the organs studied were decreasedcomparing with the normal.