From 1950 through 1975, 27 patients at the Mayo Clinic, Rochester, Minn, had coexistent psoriasis and lupus erythematosus (LE). Of the 27 patients, ten had systemic LE (SLE), 13 had discoid LE, and four had drug-induced LE or an SLE-like syndrome. The onset of psoriasis preceded LE in ten patients and was concomitant with it in six. Photosensitivity was noted in 23 patients. In 20 patients, the lesions of psoriasis and LE remained clinically distinct. Morphologic overlap and clinical interaction occurred in seven patients in whom the disorders were severe and complicated by a third disease. Generally, this latter group had extensive psoriasis, prominent photosensitivity, and a poor response to therapy.