The treatment of seminoma (stages A, B1 and B2) with conventional x-ray therapy can be expected to give satisfactory cure rates. However, the cure rate for patients with advanced stages of B3 and C disease, treated with conventional radiation therapy, is unacceptable (22 per cent). It appears that with a pre-radiation/chemotherapeutic plan consisting of actinomycin D, vincristine and cyclophosphamide survival can be improved dramatically in these patients. After a rest period of 2 to 4 weeks radiation therapy is given to the retroperitoneal, mediastinal and supraclavicular lymph nodes as per standard therapy. If evidence of bulk disease persists or if positive alpha-fetoprotein or beta-human chorionic gonadotropin has been detected then retroperitoneal lymph-adenectomy should be done after completion of the radiation therapy. With adjuvant chemotherapy 5 of 5 patients survive free of disease 18 months to 5 years after therapy.