Seventy-two children with recurrent, progressive, or metastatic lymphomas and other solid tumors, exclusive of primary central nervous system (CNS) tumors, were treated with aziridinylbenzoquinone (AZQ, diaziquone) at 9 mg/m2/day by 30-min intravenous infusion for 5 days every 3 weeks. Fifty-four patients were evaluable for response. Three partial responses occurred, two in patients with recurrent Hodgkin's disease and one in a patient with intraocular retinoblastoma. Sufficient numbers of patients with osteosarcoma, neuroblastoma, and Wilms' tumor were evaluable to demonstrate inactivity of this dosing regimen in these tumor types. Numbers of evaluable patients for other tumor types were insufficient to conclusively demonstrate inactivity. Myelosuppression, which was profound and prolonged, was observed. As administered in this study, AZQ has marginal activity and severe myelotoxicity in children with solid tumors.