The radiation protective mechanisms on skin injury induced by soft X-irradiation were investigated by use of various radiation protective agents such as sulfur compounds (MEA, MEG, thiourea), nucleic acid constitutional compounds (adenosine, inosine), antioxidative compounds (sesamol, ferulic acid, ascorbic acid), crude drugs (Rosae Fructus, Anemarrhenae Rhizoma, Trapae Fructus, Forsythiae Fructus, Aloe arborescens). Scavenge action of activated oxygen, inhibitory effect of lipid peroxidation, induction of antioxidative protein and protective effect against damage of deoxyribonucleic acid and superoxide dismutase by X-irradiation were evaluated as the radiation protective mechanisms, and relationship between these results and protective effect of skin injury induced by radiation was studied.