Patients who achieve remission after induction therapy receive 2 courses of intensification therapy, for approximately 4 months. During the first course, patients receive cytarabine IV over 3 hours twice daily on days 0, 1, 7, and 8. Patients also receive asparaginase intramuscularly on days 1 and 8. The second course of therapy comprises CNS prophylaxis. Patients with no CNS disease at diagnosis or whose CNS disease resolved by day 7 of induction therapy receive cytarabine IT on days 0, 7, and 14. Patients with persistent CNS disease on day 7 of induction therapy receive cytarabine IT, hydrocortisone IT, and methotrexate IT on days 0, 7, and 14.