We investigated the use of extracorporeal chemotherapy (photopheresis) in eight patients with cutaneous T cell lymphoma. Initially described by Edelson et al. for the treatment of erythrodermic cutaneous T cell lymphoma, we have expanded the treatment to include patients with extensive patch/plaque disease as well as tumor-stage disease. Four of five patients with erythrodermic stage disease had either a complete or a partial clinical remission with photopheresis alone. One patient with extensive patch/plaque disease continued to have a partial clinical remission of 7 months' duration with photopheresis alone. Of the two patients with tumor-stage disease, one remained without evidence of clinical disease at 10 months with photopheresis alone, whereas the second patient had a partial clinical remission of 5 months with a combination of local radiation therapy followed by monthly photopheresis. The skin biopsy specimen obtained from the patient with tumor-stage disease in complete clinical remission did not show cutaneous T cell lymphoma. We conclude that photopheresis is an effective modality alone or in combination with adjunctive therapy for erythroderma, extensive patch/plaque disease, and some tumor-stage disease.