OUTLINE: This is a randomized, multicenter study. Patients are stratified according to age, extent of resection, performance status, prior surgery, and participating center. Patients are randomized to one of two treatment arms. Arm I: Within 4-6 weeks after surgery, patients undergo radiotherapy over 7 weeks to the residual tumor volume. Arm II: Patients undergo radiotherapy as in arm I, then begin chemotherapy within 4 weeks after the completion of radiotherapy. Patients receive oral lomustine on day 1, oral procarbazine on days 8-21, and vincristine IV on days 8 and 29. Treatment repeats every 6 weeks in stable and responding patients for a total of 6 courses. Patients with disease recurrence may receive 6 additional courses of chemotherapy as above or another modality at the investigator's discretion. Patients are followed every 3 months for 1 year and then every 6 months for survival.