We conducted a multicenter study to improve the treatment of B-cell non-Hodgkin's lymphoma and acute lymphoblastic leukemia (NHL/ALL) in Japanese children. The subjects were a total of 57 untreated patients with the B-cell type of either NHL (27 Burkitt's and 9 diffuse large) or ALL between 2 and 15 years old (median: 8 years) seen between 1988 and 1994. All patients received the same cytoreductive therapy (half doses of vincristine and prednisolone) and the same first and second induction courses (vincristine, prednisolone, high-dose methotrexate, repetitive high-dose cyclophosphamide, and adriamycin). Three cycles of consolidation blocks A and B (consisting of reduced doses of similar agents used in the second induction course) followed for patients with stage III or IV NHL or B-ALL, while only one cycle was given for stage I or II disease. Fifty-three patients (93.0%) achieved complete remission. Eight patients had relapse all occurring within 1 year. Another patient had secondary myelodysplastic syndrome. The median follow-up period was 48 months (range: 24-94 months). The overall survival and event-free survival (EFS) rates for all patients were, respectively, 75.9% (S.E.: 5.9) and 70.1 (S.E.: 6.1). The relapse-free interval rate of the 53 patients who achieved CR was 83.5% (S.E.: 5.3). EFS was 75.0% (S.E.: 21.7) in stage I, 84.6% (S.E.: 10.0) in stage II, 78.63% (S.E.: 11.0) in stage III, 80.0% (S.E.: 17.9) in stage IV, and 52.4% (S.E.: 10.9) in ALL. Among the stage IV NHL and ALL patients, EFS was significantly worse in patients with initial CNS involvement than in those without it (14.3% (S.E.: 13.2) vs. 73.7% (S.E.: 10.1); P = 0.0025). In conclusion, our regimen (AT-B88) produced a more than 70% cure-rate for children with any stage of B-cell NHL/ALL without initial CNS involvement. However, a new regimen is needed for patients with initial CNS involvement.