OUTLINE: All patients receive up to six alternating courses (every 3-4 weeks) of two chemotherapy regimens: cyclophosphamide, oral dexamethasone, methotrexate with leucovorin rescue, vincristine, and doxorubicin over 5 days; and ifosfamide/mesna, oral dexamethasone, methotrexate with leucovorin rescue, vincristine, cytarabine, and etoposide over 5 days. G-CSF is given following each course until recovery of the neutrophil count. All patients receive triple intrathecal chemotherapy on day 1. Patients with CNS disease receive intrathecal therapy twice weekly until the CSF is clear, then weekly for 4 weeks, and monthly for 1 year; those who have not received prior CNS irradiation also receive whole-brain radiotherapy. Patients are followed monthly for 6 months, every 3 months for 18 months, every 6 months for 2 years, then annually.