The five-drug DCTER regimen consists of dexamethasone, 6 mg/m²/d by mouth (PO); ara-C, 200 mg/m²/d continuous infusion (CI); 6-TG, 50 mg/m² PO twice daily; etoposide, 100 mg/m²/d CI; and rubidomycin, 20 mg/m²/d CI.20 Ara-C, etoposide, and rubidomycin are mixed in a single bag. Children under 3 years receive per kilogram dosing. One course of intensively-timed DCTER is given on days 0 to 3 and 10 to 13; standard-timing DCTER is given on days 0 to 3 and after marrow recovery if the day-14 marrow has <5% blasts or on days 14 to 17 if there are 5% blasts. Patients receive two courses of induction therapy. Transplant cytoreduction consists of busulfan 1 mg/kg every 6 hours for 16 doses. Graft-versus-host prophylaxis is with methotrexate. Chemotherapy consists of Capizzi II high-dose ara-C, 3 g/m²or 100 mg/kg 3-hour intravenous infusion every 12 hours four times on days 0 and 1 and days 7 and 8; and L-asparaginase, 6,000 U/m² or 200 U/kg intramuscular at 42 hours. After marrow recovery patients receive daily 6-TG with ara-C, 75 mg/m²and 5-azacytidine at 100 mg/m² four times, and cyclophosphamide, 75 mg/m² four times for 2 months. Treatment ends with a modified DCTER regimen. Central nervous system prophylaxis is with 7 doses of intrathecal ara-C. Boxed in regimens are those used for DS patients after July 18, 1996.