Extracorporeal photochemotherapy is a new form of immunotherapy which involves the extracorporeal photoinactivation of peripheral blood cells by 8-methoxypsoralen in the presence of ultraviolet A irradiation, followed by readministration of the cells. To explore the efficacy of this therapy in the treatment of autoimmune disease, four patients with a lengthy history of corticosteroid and immunosuppressive drug-resistant pemphigus vulgaris were initiated on extracorporeal photochemotherapy. Three patients experienced a complete remission in cutaneous disease expression, permitting discontinuation of medications in two and a substantial decrease in the third. Significant reductions in serum antiepidermal cell antibody titers occurred in all four patients. The treatments were well tolerated without the occurrence of adverse events. These results in a small number of patients suggest that extracorporeal photochemotherapy may prove to be a useful tool in the treatment of aggressive autoimmune disease.