The study population included 136 patients with stage IA, IB, IIA, IIB, or IIIA1 Hodgkin's disease. The median follow-up is 7.5 years. Among the 30 patients with peripheral IA disease, all patients achieved a complete response (CR) with radiation therapy, and no patient has relapsed. Patients of other stages were randomized to receive radiation therapy or mechlorethamine, vincristine, procarbazine, and prednisone (MOPP). Among the 51 patients randomized to receive radiation therapy, 49 (96%) achieved complete remission, 17 (35%) have relapsed, and 10 (20%) have died. Fifty-two of the 54 (96%) assessable patients randomized to receive MOPP obtained CRs, seven (13%) have relapsed, and four (7%) have died. The projected 10-year disease-free survival of patients randomized to receive radiation therapy is 60%; for those randomized to receive MOPP, it is 86% (P2 = .009 in favor of MOPP). The projected 10-year overall survival for patients randomized to radiation therapy is 76%, and for MOPP-treated patients it is 92% (P2 = .051 in favor of MOPP). When the randomized patients with massive mediastinal disease or stage IIIA1 disease were excluded from the analysis, the disease-free (67% for radiation v 82% for MOPP) and overall survival (85% for radiation v 90% for MOPP) were not significantly different between the two arms. Subset analysis showed significant superiority of MOPP in the treatment of the following patient groups: stage IIIA1 or massive mediastinal disease, no B symptoms, initial erythrocyte sedimentation rate greater than 20 mm, four or more sites of disease, and younger than age 40 years. Preliminary analysis of this ongoing study shows that MOPP chemotherapy is at least as effective as radiation therapy in the treatment of the specific groups of early-stage Hodgkin's disease patients randomized. The final assessment of these two diverse treatment options will depend largely on the long-term survival and the incidence of early- and late-treatment complications for which patients are continuing to be observed.