Mercaptopurine will be substituted for thiopurine in TPMT HET/deficient patients Dexamethasone (for ETP immunophenotype only) 10 mg/m2/day PO (divided t.i.d.)Days 1-21; 4 mg/m2/day PO (divided t.i.d) Days 22-24; 2 mg/m2/day PO(divided t.i.d) Days 25-28 Vincristine 1.5 mg/m2 IV (max 2 mg) Days 1, 8, 15, 22 Daunorubicin 25 mg/m2 IV Days 1 and 8 PEG-asparaginase 3,000 Units/m2 IV Day 3