Six cycles of mechloretamine, vincristine, procarbazine and prednisone (MOPP) chemotherapy were randomly compared with extended field radiotherapy (RT) in 89 adult patients with pathological stage I-II A Hodgkin's disease (HD). 45 patients received RT and 44 were treated with MOPP. Complete remission (CR) was obtained in all patients in the RT group and in 40 of 44 in the MOPP group. 12 patients relapsed in both groups. 10 out of 44 patients treated with MOPP died of HD, compared with only 2 in the RT group. 3 more patients died in the MOPP group following the occurrence of second cancers. 11 out of the 12 (96%) patients relapsing after RT achieved a second CR, compared with 6 out of the 12 (50%) patients relapsing after MOPP. Analysis of the response rate with salvage treatment, shows that, of the 12 patients who relapsed after MOPP, the pattern of relapse might predict the likelihood of achieving a second CR, whereas in the RT group a second CR was achieved regardless of the characteristics of relapse. Survival probability for relapsing patients at 80 months calculated from relapse was 85% in the RT group and 15% in the MOPP group (P = 0.02). With a median follow-up of more than 8 years, the overall survival of patients was significantly better for RT compared with MOPP; 93 and 56%, respectively (P < 0.001). On the basis of these results we conclude that, to date, RT alone remains the treatment of choice for adult patients with early-stage HD with favourable prognostic factors.