One hundred fifteen untreated patients with supra-diaphragmatic, pathologically staged (PS) IA-IIB Hodgkin's disease (HD) were entered into a randomised study comparing treatment using mantle radiotherapy followed by adjuvant treatment with mustine, vinblastine, prednisolone, and procarbazine (MVPP) with mantle radiotherapy alone. Fifty-six patients were randomised to receive radiotherapy alone (RT) and 59 to radiotherapy followed by six cycles of adjuvant MVPP (RT + MVPP). One hundred fourteen patients achieved a complete remission (CR) with radiotherapy. One patient achieved a partial remission. The overall 10-year survival after correction for intercurrent death was 92% with no difference between the two treatment groups (90% for RT alone and 95% for RT + MVPP P = 0.66). There were 9 (8%) deaths from HD (5 patients had received RT alone), and 10 (9%) intercurrent deaths. Eight (7%) patients have developed a second malignancy, and two of them are alive. No patient has developed secondary acute myelogenous leukaemia. The 10-year relapse-free survival (RFS) was 79% overall, 67% in the RT group, and 91% in the RT + MVPP group (P = 0.0004). There were 25 relapses; 20 patients had received RT alone and 5 had received adjuvant MVPP. Of the relapsed patients, 13 (52%) have received successful salvage therapy and are in CR. In the RT alone group, 45 (80%) patients are alive in CR, 5 (9%) died of HD, and 6 (11%) died of intercurrent causes. In the adjuvant MVPP group, 51 (86%) are alive in CR, 4 (7%) died of HD, and 4 (7%) died of intercurrent causes.(ABSTRACT TRUNCATED AT 250 WORDS)