Untreated patients with Hodgkin's lymphoma in stages I-IIIA with risk factors (large mediastinal mass, massive splenic involvement, extranodal disease) were entered into the HD1 protocol and received a combined chemo-radiotherapy [2 X (COPP + ABVD) + 40 Gy extended field irradiation (EF) vs 2 X (COPP + ABVD) + 20 Gy EF]. Patients in stages IIIB/IV (HD3 protocol) received induction chemotherapy [3 X (COPP + ABVD)] and were randomized into consolidation by radiotherapy [20 Gy involved field irradiation (IF)] vs chemotherapy [1 X (COPP + ABVD)]. Seventy-three of 89 evaluable patients (82%) treated according to the HD1 protocol achieved a complete remission. Freedom from progression and survival of patients in stages I-IIIA with risk factors treated according to HD1 were no worse than those of patients in stages I and II without risk factors who received only radiotherapy. Eighty-six of 137 patients (63%) treated according to the HD3 protocol achieved complete remission after induction chemotherapy with COPP + ABVD. This is significantly better than the 31% complete remission rate observed in a previous pilot study with COPP alone (P less than 0.01). Including salvage therapy (radiotherapy in case of persisting nodal disease; chemotherapy with 4 X CEVD in case of persisting disseminated disease), a total of 76% complete remissions in stages IIIB/IVAB were achieved. A high erythrocyte sedimentation rate (greater than 80 mm h-1) was the most significant risk factor for achieving freedom from progression.