OUTLINE: Patients receive induction therapy on days 1-28. Patients receive supportive oral prednisolone daily for three doses during weeks 1-4, vincristine IV weekly for 5 weeks starting on day 1, asparaginase intramuscularly or subcutaneously three times a week beginning on day 4, and methotrexate intrathecally on days 1 and 8. Patients who meet certain criteria are given first intensification therapy beginning on day 29. Patients receive three doses of oral prednisolone, vincristine IV on day 1, daunorubicin IV over 6 hours on days 1 and 2, etoposide IV over 4 hours on days 1-5, cytarabine IV every 12 hours by bolus injection on days 1-5, oral thioguanine daily on days 1-5, and methotrexate intrathecally as in induction therapy. Patients are followed at 8 weeks. Those patients who experience remission receive a third intensification block at 35 weeks. All patients receive three methotrexate infusions followed by continuation therapy beginning at week 14. As continuation therapy, patients receive oral mercaptopurine daily, oral methotrexate weekly, vincristine IV every 4 weeks, oral prednisolone for 5 days every 4 weeks, and intrathecal methotrexate every 12 weeks beginning at week 23 until 100 weeks from the start of treatment. Continuation therapy will be interrupted at about week 20 for the second intensification therapy. For second intensification therapy, patients receive oral prednisolone daily for 5 days, a single dose of vincristine on day 1, daunorubicin IV over 6 hours on days 1 and 2, etoposide IV over 4 hours on days 1-5, bolus injections of cytarabine every 12 hours on days 1-5, oral thioguanine daily on days 1-5, and intrathecal methotrexate as in induction therapy. Continuation therapy re-starts at week 23. Patients who receive the third intensification therapy will begin at week 35. For the third intensification therapy, patients receive three doses of oral dexamethasone, IV vincristine on day 1 of weeks 35-38, subcutaneous asparaginase for 9 days during weeks 35-38, intrathecal methotrexate on day 1 of weeks 35 and 39, IV cyclophosphamide on day 1 of weeks 39 and 41, subcutaneous or IV cytarabine daily on days 1-4 of weeks 39- 42, and oral thioguanine daily during weeks 39-42. Continuation therapy re-starts at week 42/43. Some patients may receive radiotherapy during chemotherapy. Patients are followed every month for 1 year, every 2 months for the next year, every 6 months for the next 3 years, then annually thereafter.