Twenty-nine patients were treated with 31 courses of high-dose combination cyclophosphamide, cisplatin, and carmustine (BCNU) with and without melphalan with autologous bone marrow support. Toxicity was dose related. The maximum tolerated dose for cyclophosphamide, cisplatin, and BCNU in this combination in mg/m2 was 5,625, 165, and 600, respectively. Further dose escalation was precluded by the development of multiple organ toxicity, including venoocclusive disease, refractory thrombocytopenia, and hypertension. Melphalan added to the three-drug combination produced excessive renal and gastrointestinal toxicity. Objective tumor regression occurred in 21 of 25 evaluable cases. The results suggest that selected alkylating agents can be combined in full or nearly full doses before nonmyelosuppressive dose-limiting toxicity precludes further escalation.