OUTLINE: This is a randomized study. Patients are stratified according to participating institution. The following acronyms are used: ARA-C Cytarabine, NSC-63878 ASP Asparaginase (E. coli), NSC-109229 CTX Cyclophosphamide, NSC-26271 DM Dexamethasone, NSC-34521 DNR Daunorubicin, NSC-82151 DOX Doxorubicin, NSC-123127 HC Hydrocortisone, NSC-10483 MP Mercaptopurine, NSC-755 MTX Methotrexate, NSC-740 PEG-ASP Pegaspargase, NSC-624239 PRED Prednisone, NSC-10023 TG Thioguanine, NSC-752 TIT Triple Intrathecal Therapy (IT MTX/IT ARA-C/IT HC) VCR Vincristine, NSC-67574 Induction: All patients receive oral PRED on days 0-27, VCR IV on days 0, 7, 14, and 21, and ASP IM 3 times a week for 3 weeks beginning on day 2-4. ARA-C IT is administered on day 0, and MTX IT is administered on days 7 and 28 (days 7, 14, 21, and 28 if CNS disease at diagnosis). Following Induction, patients who achieve remission are randomly assigned to 1 of 4 treatment arms. Arm I: Consolidation (begins day 28 of Induction): PRED is tapered from Induction over 10 days. Patients receive VCR IV on day 0, oral MP on days 1-27, and MTX IT on days 7, 14, and 21 (only day 7 if CNS disease at diagnosis). Interim Maintenance 1 (begins day 28 of Consolidation): Patients receive oral PRED on days 0-4 and 28-32, VCR IV days 0 and 28, oral MTX on days 0, 7, 14, 21, 28, 35, 42, and 49, and oral MP on days 0-49. Delayed Intensification 1 (begins day 56 of Interim Maintenance 1): Patients receive oral DM on days 0-6 and 14-20, VCR IV on days 0, 7, and 14, DOX IV over 15-120 min on days 0, 7, and 14, ASP IM twice a week for 2 weeks beginning day 2-4, CTX IV over 20-30 min on day 28, oral TG on days 28-41, ARA-C IV or SC on days 29-32 and 36-39, and MTX IT on days 0, 28, and 35. Interim Maintenance 2 (begins day 56 of Delayed Intensification 1): Patients receive PRED/VCR/MTX/MP as in Interim Maintenance 1. Delayed Intensification 2 (begins day 56 of Interim Maintenance 2): Patients receive DM/VCR/DOX/ASP, CTX/TG/ARA-C, and MTX IT as in Delayed Intensification 1. Maintenance (begins day 56 of Delayed Intensification 2): Patients receive oral PRED on days 0-4, 28-32, and 56-60, VCR IV on days 0, 28, and 56, oral MP on days 0-83, oral MTX on days 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, and 77 (omitted during wk of IT therapy), and MTX IT on day 0. Treatment continues every 84 days for 2 years (girls) or 3 years (boys) from the beginning of Interim Maintenance 1. Arm II: Patients receive treatment as in arm I, except TIT is TIT substituted for MTX IT. Arm III: Patients receive treatment as in arm I with oral TG substituted for oral MTX in Consolidation, Interim Maintenance 1 and 2, and Maintenance. If secondary veno-occlusive disease occurs, MP is substituted for TG during Maintenance. Arm IV: Patients receive treatment as in arm III with TIT substituted for MTX IT. If secondary veno-occlusive disease occurs, MP is substituted for TG during Maintenance. Patients with M3 marrow after 2 weeks or M2 marrow after 4 weeks of Induction, or with Philadelphia chromosome (t[9;22][q34;q11]), t(4;11)(q21;q23), or hypodiploidy, proceed to the following more intensive treatment regimen for further therapy: Induction (begins day 14 to day 19 of initial Induction): Patients receive oral PRED on days 14-27, VCR IV on days 14 and 21 (day 14 dose omitted if day 14 dose from original Induction already given), DNR IV continuously on days 14-16 (48 hours total), ASP IM three times a week for 9 total doses (including those received on original Induction), MTX IT on days 28 and 35 (days 21, 28, and 35 if CNS disease at diagnosis). Patients with M1/M2 bone marrow after day 35 proceed to Consolidation. Consolidation (begins day 28 or 35 of Induction in this regimen, depending on timing of entry on this regimen): PRED is tapered from Induction over 10 days. Patients receive CTX IV 20-30 minutes on days 0 and 28, oral MP on days 0-13 and 28-41, ARA-C IV or SC on days 1-4, 8-11, 29-32, and 36-39, VCR IV on days 14, 21, 42, and 49, PEG-ASP IM on days 14 and 42, and MTX IT on days 7, 14, and 21 (only day 7 if CNS disease at diagnosis). Patients with M1 or M2 marrow and no extramedullary leukemia after day 63 proceed to Interim Maintenance 1. Interim Maintenance 1 (begins day 63 of Consolidation): Patients receive VCR IV on days 0, 10, 20, 30, and 40, MTX IV on days 0, 10, 20, 30, and 40, and PEG-ASP IM on days 1 and 21. Patients with M1 bone marrow after day 56 proceed to Delayed Intensification I. Delayed Intensification 1 (begins day 56 of Interim Maintenance 1): Patients receive oral DM on days 0-6 and 14-20, VCR IV on days 0, 7, 14, 42, and 49, DOX IV over 15-120 minutes on days 0, 7, and 14, PEG-ASP IM on days 3 and 42, CTX IV over 20-30 minutes on day 28, oral TG on days 28-41, ARA-C IV or SC on days 29-32 and 36-39, and MTX IT on days 28 and 35. Interim Maintenance 2 (begins day 56 of Delayed Intensification 1): Patients receive VCR/MTX/PEG-ASP as in Interim Maintenance 1, and MTX IT on days 0, 20, and 40. Delayed Intensification 2 (begins day 56 of Interim Maintenance 2): Patients receive DM/VCR/DOX/PEG-ASP, CTX/TG/ARA-C, and MTX IT as in Delayed Intensification 1. Maintenance (begins day 56 of Delayed Intensification 2): Patients receive PRED/VCR/MP/MTX, and MTX IT as in arm I Maintenance. Patients with CNS or testicular involvement at diagnosis receive appropriate radiotherapy concurrent with Consolidation. Radiotherapy begins within 4 days of initiation of Consolidation. Craniospinal irradiation is given 5 days a week. Testicular irradiation is given to both testes 5 days a week over 2-3 weeks. Patients are followed every 6-8 weeks during year 1, every 3 months during year 2, every 6 months during year 3, and then annually thereafter.