OUTLINE: Patients are stratified by CD4 count (50/mm3 and under vs greater than 50/mm3). Patients receive oral lomustine on day 1 and oral procarbazine on days 1-10 and days 22-31. Filgrastim (G-CSF) is administered subcutaneously daily on days 12-21 and days 33-42, until absolute neutrophil counts recover. Patients with a complete response after 6 weeks receive one additional course of chemotherapy prior to radiotherapy. Patients with a partial response, stable disease, or disease progression after 6 weeks proceed to radiotherapy without receiving a second course of chemotherapy. Whole brain radiotherapy is administered daily for 28 days beginning 1-3 weeks following chemotherapy. Quality of life is assessed prior to therapy, at 3 and 6 weeks, and then every 2 months following radiotherapy. Patients are followed every 2 months until death.