In a multicenter study in which data from all Hodgkin's disease patients in Denmark have been registered since 1971, all patients with supradiaphragmatic stage I and II disease (as confirmed by staging laparotomy) were randomized to receive either radiotherapy (RT) to supradiaphragmatic and infradiaphragmatic lymph node regions (total nodal irradiation) or RT to a mantle field followed by six cycles of MOPP combination chemotherapy (CT) (RT plus CT). Interim results up to July 1980, when 261 patients had entered the study, showed 28 failures among 128 patients in the total nodal irradiation group and four failures among 133 patients in the RT plus CT group (P less than 0.05). Stage II, nodular sclerosing or mixed cellular histology, and gross hilar/mediastinal involvement defined subsets of patients in the RT group with a relatively high relapse frequency. Salvage treatment of the relapsed patients has so far been good and there is as yet no difference in overall survival. However, longer observation time is needed before the cure rate can be evaluated with certainty. Two patients treated with RT alone and one treated with RT plus CT developed acute myeloid leukemia.