Induction: Patients receive idarubicin IV over 30 minutes on days 0-3, cytarabine and etoposide IV continuously on days 0-3, and oral thioguanine twice a day and oral dexamethasone 3 times a day on days 0-3. Patients then begin course 2, which consists of cytarabine, etoposide, thioguanine, and dexamethasone on days 10-13, daunorubicin IV continuously on days 10-13, and filgrastim (G-CSF) subcutaneously (SC) beginning on day 16 and continuing until blood counts recover. Patients also receive CNS prophylaxis/therapy consisting of cytarabine intrathecally (IT) on days 0 and 14 (if no CNS disease at entry) or on days 0, 5, and 7 (if CNS disease present at entry). Disease is reassessed on day 28-42. Patients with M1 or M2 marrow proceed to consolidation while those with M3 marrow or progressive disease go off study.