A series of experiments was performed to determine whether agents which alter the effects of ultraviolet light might favorably influence the survival rate after total-body exposure to ionizing irradiation. Antimalarials, psoralen, benzophenones, and a benzotriazole were administered in the diet to albino mice before irradiation. The results were inconclusive but suggested that certain agents of this type may be capable of providing some degree of protection and that further experimentation and evaluation would be justified. The need for research on practical methods for protecting man from the effects of excessive radiation is emphasized. To date the sulfhydryl compounds have shown the most promise for this purpose.