To address the problem of drug dosage as a limiting factor for successful chemotherapy, seven patients with Stage IV neuroblastoma were treated with very high dose cyclophosphamide with imidazole carboximide (DTIC) and vincristine sulfate in conjunction with intensive supportive care. None of the patients experienced a complete response. The major toxicity was myelosuppression, complicated by significant infections. Toxicity was significantly more severe in this study than in similar regimens using these three drugs at conventional doses. Although the number of patients in this study was small and most had received prior therapy, our data do not support the efficacy of very high dose cyclophosphamide in the treatment of Stage IV neuroblastoma.