A phase-II study of ifosfamide with mesna, given intravenously daily for five days by bolus injection, has demonstrated the activity of ifosfamide against a spectrum of childhood malignant solid tumors. Ifosfamide presently is being investigated in alternative phase-I schedules, daily times three or every other day times three with the aim of delivering comparable amounts of ifosfamide without increasing toxicity--specifically, neurotoxicity. Additionally, response following ifosfamide treatment is being evaluated for previously untreated children with osteosarcoma and rhabdomyosarcoma after 6 weeks of treatment, and for previously untreated patients with Ewing's sarcoma after 9 weeks of treatment with ifosfamide/VP-16 (etoposide) given in combination.