OUTLINE: Patients who do not achieve M1/M2a marrow following Induction proceed to Salvage Induction; all others proceed to Intensification. Patients receive Consolidation therapy on Regimen A, B, or C according to the investigator's choice. The following acronyms are used: ARA-C Cytarabine, NSC-63878 2-CdA Cladribine (2-Chlorodeoxyadenosine), NSC-105014 DHAD Mitoxantrone, NSC-301739 G-CSF Filgrastim, NSC-614629 HC Hydrocortisone, NSC-10483 HD High Dose MTX Methotrexate, NSC-740 PBSC Peripheral Blood Stem Cells TBI Total-Body Irradiation TIT Triple Intrathecal Therapy (IT ARA-C/IT HC/IT MTX) VP-16 Etoposide, NSC-141540 INDUCTION: 2-Drug Combination Chemotherapy plus CNS Prophylaxis/Therapy. ARA-C/DHAD; G-CSF; plus IT ARA-C and, if CNS disease at entry, TIT. SALVAGE INDUCTION: 2-Drug Combination Chemotherapy. 2-CdA/VP-16. INTENSIFICATION: 2-Drug Combination Chemotherapy followed, as indicated, by Radiotherapy. HD ARA-C/VP-16; followed, in patients with persistent CNS disease, CNS relapse, or chloromas, by irradiation using megavoltage equipment (minimum Co60 and maximum 6 MV x-rays or electrons). CONSOLIDATION: Regimen A: 2-Drug Combination Chemotherapy. 2-CdA/VP-16. Regimen B: Myeloablative Chemoradiotherapy followed by Hematopoietic Rescue. TBI (equipment unspecified) with electron boosts to the testes, chest, extramedullary sites, and, if indicated, craniospinal region; VP-16; followed by allogeneic or autologous bone marrow or PBSC. Regimen C: No further therapy.