Gamma-radiolysis of 0.05 M neutral proline solution was investigated. As the main reaction of proline radiolysis in oxygenated solutions, the hydroxylation reactions leading to hydroxyproline formation and the reactions leading to the total destruction of the pyrrolidine ring were shown. In oxygen-free solutions the yield of these reactions decreased; in this medium combination reactions giving rise to higher molecular weight combination products (up to approx. 1500) belong to the most important ones. In addition to radiation-decarboxylation reactions the products of radiation-carboxylation reactions were also detected in the irradiated solution of proline free of oxygen.