A phase II trial of a single 5-day course of deferoxamine in 9 patients with neuroblastomas was completed. Within 2 days of completion of treatment responses were observed in 7 of 9 patients and there was no drug toxicity. These responses were a decrease in bone marrow infiltration and, in one patient, a measurable reduction in her tumor mass. We conclude that deferoxamine given as an 8-h i.v. infusion daily for 5 days at 150 mg/kg/day has antitumor activity.