Patients with resected stage I and resected abdominal-only stage II disease are treated on the Group A Regimen. Patients with unresected stage I/II, stage III, or CNS-negative stage IV disease with fewer than 25% blasts in bone marrow are treated on the Group B Regimen. Patients with 25% or more blasts in bone marrow or with CNS involvement (i.e., L3 blasts in CSF, cranial nerve palsy, clinical spinal cord compression, isolated intracerebral mass, or parameningeal cranial or spinal extension) are treated on the Group C Regimen.