The H5 program in clinical stage (CS) I to II supradiaphragmatic Hodgkin's disease (HD) was tailored to prognostic factors identified in former European Organization for the Research and Treatment of Cancer (EORTC) studies. Among the 494 adult patients included in the study, the 237 patients belonging to the favorable group (H5F) underwent a staging laparotomy (Sx) in order to select the patients who could be treated with limited radiotherapy (RT) only. Thus, 198 patients (84%) with negative laparotomy were treated with RT alone and randomized to either mantle irradiation (M) or extended field mantle plus para-aortic (M + PA) irradiation. Complete remission (CR) was achieved in 99% of the patients. There was no difference in the 6-year relapse-free survival (RFS) rate (74% and 72%, respectively) or survival rate (96% and 89%). Therefore, Sx helped to define those patients who could be treated with M alone in contrast to those who required more aggressive therapy. The 39 patients with positive laparotomy were treated as the unfavorable group (H5U) from onset and randomized to either total/subtotal nodal irradiation (TNI/STNI) or a sandwiched mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) X 3, M irradiation, MOPP X 3 protocol (3M). Although the RFS rate was higher in the 3M arm (100% v 53%; P = .002), the 6-year survival was not significantly different between the two arms (overall, 92%). In the 257 patients with initial unfavorable disease, the Sx was avoided. They were randomized to either TNI/STNI or 3M. In complete responders (96%), the 6-year RFS was 91% in the 3M arm and 77% in the TNI/STNI arm (P = .02). The pattern of failure differed in the two arms: the inverted Y and spleen irradiation controlled occult infradiaphragmatic disease better than MOPP; conversely, less patients begun on MOPP recurred in the involved mantle areas. The difference in 6-year actuarial total survival (TS) (89% and 82%; P = .05 in favor of the 3M arm) was not retrieved after exclusion of the unrelated deaths from the analysis. The two arms produced similar TS in patients under 40 years of age. TNI retains interest, especially in young men wishing to preserve fertility. The overall result shows that when treatment is tailored to initial prognostic factors, excellent results can be obtained in all patient subgroups at minimal morbidity and toxic cost.