Investigation results in a group of 14 cases of photosensitive psoriasis (p.p.) were compared with findings from a group of the same number suffering from ordinary p. In p.p. there is a higher percentage of subjects with light hair and skin and the erythema threshold for UV-light is somewhat lower. The disease is regularly and distinctly localized on places not covered by clothing, made worse by insolation and spontaneously improves during the winter months. It is only exceptionally that photosensitivity dates from the commencement of the disease. In contrast to ordinary p. which in the majority deteriorates after antimalarial drugs, p. p. reacts favorably to this treatment.