 - CNS therapy SR patients: Patients receive vincristine IV on day 1; oral mercaptopurine once daily on days 1-14; oral dexamethasone twice daily on days 1-5; and TIT twice weekly for 2 weeks. Patients also receive IV-PEG OR IM-EC as above beginning on day 1 and continuing for up to 30 weeks. Patients proceed to consolidation II after day 21. 