[en] The present condition of onset of injuries following radiotherapy was summarized and their controlling measures were discussed. From the analysis of radiotherapeutic cases, Umegaki pointed out that both the survival rate and the rate of onset of injury rose and that the tolerance dose of normal tissues decreased as the irradiation volume increased. In relation to the radiosensitivity of normal tissues, acute injury manifests itself in the typical cell reproduction system, and acute to late injuries manifest themselves in the conditional cell reproduction system and the non-cell reproduction system. From the standpoint of clinician, the author arranged the balance between injury and therapeutic result and measures to control injury. (Chiba, N.)