Results are presented on investigations of diethone--a new pharmaceutical to prevent and treat radiogenic skin injuries. Diethone is a synthetic antioxidant of the dihydropyridine-line. In experiment on animals the preparation was used in form of an ointment. Irradiation was done with beta- and soft roentgen rays in doses of 20 to 60 Gy on conditions of a tele- or contact radiotherapy. A reduction of intensity and duration of radio reactions by more than 50% and a slighter occurrence of radio reactions were shown. The protecting effect of diethone is much stronger than that of mexamine, cystamine and other radioprotectors. Application of this preparation in treatment of radiogenic dermatitides results in relief of inflammation appearances, in shortening of recovery-time, and in accelerated skin regeneration. The intravital investigations of skin by means of contact-luminescence-microscope and investigations using light- and electron-microscopy did not give any alterations in structure of regenerated skin in diethone-treated animals compared with control. Also a better conservation of protected intracellular membranes especially of mitochondrial membranes were seen. Generally penetration of 14C-diethone into skin occurs within two hours after application of ointment. It can not be found hardly within inner media.