In 13 patients with therapy-resistant solid tumors the feasibility of high-dose cyclophosphamide (7 g/m2) in combination with increasing doses of VP 16-213 with autologous bone marrow transplantation was studied. Dose-limiting extramedullary toxicity appeared to be mucositis and occurred after 2.5 g/m2. Two toxic deaths were observed in patients older than 55 yr. Responses were seen in eight out of nine evaluable patients. Two patients with ovarian cancer still have no signs of disease progression after 12+ months. High-dose cyclophosphamide (7 g/m2) can be combined with VP 16-213 1.5 g/m2 without important extramedullary toxicity. Age is probably a limiting factor for this kind of therapy.