Mercaptopurine 75 mg/m2 PO, daily x 7 days, Days 1-7 Methotrexate 40 mg/m2 IV or IM, Day 1 Cyclophosphamide 300 mg/m2 IV, Day 1 Cytarabine 300 mg/m2 IV, Day 1 Dexamethasone 12 mg/m2 (std/high risk) or 8 mg/m2 (low risk) PO daily (tid) x 5, Day 1-5 Vincristine 2.0 mg/m2 IV push (max. 2 mg), Day 1