Four patients with psoriasis were treated with continuous ambulatory peritoneal dialysis (CAPD). Two were being treated for renal failure; the other two had normal renal function and were being treated exclusively for psoriasis. With CAPD at a rate of three to four exchanges per day, the psoriasis cleared completely in the two patients with renal failure and improved in the other two. In the patients without renal failure, low-flow peritoneal dialysis (one exchange per day) seemed to be of some value in maintaining remission but was ineffective in treating more active disease. Long-term therapy (greater than or equal to 12 weeks) with three or four daily exchanges may be needed for initial complete remission, and continuous treatment may be needed to prevent relapse. Thus, CAPD shows promise for the study of psoriasis and may be a last-resort treatment for severe, disabling cases.