OUTLINE: This is a multicenter study. Patients are stratified according to disease (chronic myelogenous leukemia vs acute lymphoblastic leukemia vs acute myelogenous leukemia). Patients receive cytarabine IV over 4 hours, etoposide IV over 1.5-2 hours, and idarubicin IV over 5-10 minutes on days 1, 3, and 5. Filgrastim (G-CSF) is administered subcutaneously (SC) daily beginning on day 2 and continuing until blood counts recover. Chronic myelogenous leukemia: On day 14 following chemotherapy, if bone marrow biopsy shows less than 20% cellularity and a peripheral blood sample contains greater than 50% cytogenetically normal cells, patients receive a second induction course followed by apheresis. Patients with less than 50% cytogenetically normal cells are also considered for a second induction course. Patients with no response or progressive disease are removed from the study. Acute leukemia: On day 14 following chemotherapy, if bone marrow biopsy shows less than 20% cellularity and the peripheral blood sample shows 100% cytogenetically normal cells, patients receive a second induction course followed by apheresis. Patients with high risk disease in first remission at time of study entry undergo apheresis during recovery from first course of induction therapy and second course may be omitted. Patients receive second induction course followed by G-CSF as after first induction course. Once blood counts recover, patients undergo harvest of peripheral blood stem cells (PBSC). Patients also undergo bone marrow stem cell collection in case of failure of PBSC transplantation (PBSCT). Patients receive the following conditioning regimen: total body irradiation twice a day on days -8 to -5; etoposide IV over 4 hours on day -4; and cyclophosphamide IV over 2 hours on day -2. PBSCT is conducted on day 0. G-CSF SC is administered beginning on day 1 and continues until blood counts recover. Patients receive maintenance therapy with interferon alfa SC 3 times a week for 12 months. Patients are followed weekly for 3 months and then monthly until death.