In this phase III trial, 770 patients with clinical stage I-II Hodgkin's disease (HD) have been enrolled since November 1988. Preliminary results are given for the 605 (79%) patients who have completed their initial therapy. Patients were grouped according to 6 pretreatment prognostic characteristics. In the very favourable (VF) group, treatment consisted of mantle field alone. In the favourable (F) group, patients were randomized to either subtotal nodal irradiation (STNI), or 6 cycles of EBVP (epirubicin, bleomycin, vinblastine, prednisone) followed by involved-field irradiation (IF-RT). Unfavourable (U) patients were randomized to either 6 cycles of EBVP plus IF-RT, or to 6 cycles of MOPP/ABV hybrid plus IF-RT. Of the 35 VF patients, none have progressed during radiotherapy. Four patients relapsed and were salvaged. Three-year failure-free survival (FFS) was 82%; overall survival (OS) was 100%. Of the 254 F patients, 130 were treated with STNI and 124 with EBVP plus IF-RT. At 3 years, FFS rates were 81% (1 progression, 14 relapses) and 79% (5 progressions, 8 relapses), respectively. Corresponding OS rates were 99% and 100%. Of the 316 U patients, 160 received EBVP and 156 MOPP/ABV. At 3 years, FFS rates were 72% (18 progressions, 20 relapses) and 88% (7 progressions, 6 relapses), respectively (p < 0.001). Although OS rates were identical (92%), the entry in the U-EBVP arm was stopped in November 1992. We conclude that a treatment strategy based on prognostic factors allows the use of less aggressive treatment in favourable patients.(ABSTRACT TRUNCATED AT 250 WORDS)