The efficacy of a combination treatment with interferon alpha-2a and photochemotherapy was investigated in 16 patients with cutaneous T cell lymphoma. During the initial treatment, interferon alpha-2a was given subcutaneously at maximum dose of 9 million IU. Simultaneously, photo-chemotherapy with a maximum single dose of 3.0 J/cm2 was applied. After a complete or partial remission had been achieved, the dose of interferon was continued as permanent treatment at 3-9 million IU a week. Photochemotherapy was maintained twice a week for a minimum of 2 months and then stopped depending on the course of the disease. The combination treatment was well tolerated and all patients responded to the initial therapy. Three patients were withdrawn at an early stage of therapy, as they developed erythrodermia after photochemotherapy. The permanent treatment led to a complete remission in ten out of 13 patients and to a partial remission in three patients. During the follow-up period (now 10-40 months), therapy was stopped in four patients because of progression and in one patient because of newly diagnosed Hodgkin's disease. In another three patients, who developed local recurrences, a repetition of the initial treatment schedule was necessary to keep them in remission.