The aims of trial NHL-BFM 90 for patients (pts) suffering from B-cell neoplasms are to prove whether: 1. Treatment for pts with complete resection can be reduced from 3 to 2 therapy courses; 2. Results for pts of stage III with large abdominal tumors can be improved by high dose (HD) chemotherapy; 3. Survival for pts with incomplete initial response can be improved by therapy intensification; 4. Intraventricularly applied CNS chemotherapy can improve the outcome for CNS positive pts. Therapy is stratified into 3 branches. Branch 1: completely resected; branch 2: not resected, extra-abdominal localization only or abdominal localization and LDH < 500 U/l; branch 3: abdominal localization and LDH > or = 500 U/l, and all pts with BM or/and CNS involvement or multifocal bone disease. A 5-day prephase is followed by 2 (R1), 4 (R2), 6 (R3) therapy courses composed of dexamethasone (DEXA), methotrexate (MTX) 5 g/m2/24 h (in branch R1, 500 mg/m2), MTX/Cytarabine (ARA-C)/prednisolone (PRED) i.th., vincristine (not in branch R1), ifosfamide alternating with cyclophosphamide, ARA-C/etoposide (VP16) alternating with doxorubicin. CNS pos. pts receive MTX/ARA-C/PRED applied intraventricularly. Pts with incomplete response after 2 courses receive an intensification (DEXA, Vindesine, HD-ARA-C, VP16, and MTX/ARA-C/PRED i.th.). Pts with viable tumor after the intensified course receive mega-dose chemotherapy with autologous BM rescue (aBMT). From 4/1990 to 12/1992, 228 pts were registered; 212 pts are evaluable for response. The probability of event free survival (pEFS) at 3 years is 89 +/- 2% for the whole group, 97 +/- 3% for pts of branch R1 (n = 32), 99 +/- 1% for patients of branch R2 (n = 87), and 77 +/- 4% for patients of branch R3 (n = 94) (median observation time 21 months). 7 pts of branch R3 died early due to infections. 15 pts failed therapy (one pt each in branch R1, and R2, 13 pts in branch R3). pEFS for pts with stage III abdominal disease and LDH > or = 500 U/l is 80 +/- 6 as compared to 53 +/- 8% in the preceding studies (p < .02). Of 13 evaluable pts with CNS disease 3 died early of infection, however none suffered from relapse. Only 1 of 22 pts of branch R2 who had residual tumors after 2 therapy courses suffered from progress in contrast to 9 of 33 such pts of branch R3. Only 2 pts had viable tumor after the intensification course CC. They received aBMT, both are in CCR.(ABSTRACT TRUNCATED AT 400 WORDS)