During the period June 1984 through February 1989, 207 children, newly diagnosed with standard-risk acute lymphoblastic leukemia (ALL), were treated with the Tokyo Children Cancer Study Group L84-11 protocol. The patients were randomized into two regimen groups (S1 and S2). All patients received identical induction therapy with vincristine, prednisolone, and L-asparaginase. For central nervous system (CNS) prophylaxis, the patients in regimen S1 received cranial irradiation (18 Gy) and intrathecal chemotherapy starting at 5 weeks, while those in regimen S2 received this therapy starting at 24 weeks. Consolidation consisted of cyclic therapy with vincristine and dexamethasone, and then, after 128 weeks, with medium-dose methotrexate, CNS chemoprophylaxis, and dexamethasone. Regimen S2 employed early consolidation with three doses of medium-dose methotrexate and CNS chemoprophylaxis. The treatment duration was 3.5 years. Complete remission was achieved in 96.0% and 99.0% of the patients in regimens S1 and S2, respectively. Event-free survival (EFS) rates were 80.0 +/- 3.5% in total, 74.5 +/- 5.7% in regimen S1, and 85.1 +/- 5.7% in regimen S2 at a median follow-up of 42 months (< 85 months). There was no significant difference in the EFS between the two regimens. As compared with recently reported results of treatment for this disease, our protocol can yield similar EFS rates with mild toxicity.