Here we report the long-term results of the DCLSG protocols ALL-6 and -7 with special emphasis on the incidence of CNS relapse after treatment without cranial irradiation. In DCLSG protocol ALL-6 (1984-1988), designed for patients with ALL non-high risk (ALL-NHR) (WBC <50 x 10(9)/l, no mediastinal mass, no B cell phenotype and no CNS involvement at diagnosis, comprising 71% of all ALL patients), CNS prophylaxis consisted of a combination of three methods of chemotherapeutic CNS prophylaxis (the use of dexamethasone during induction and maintenance therapy, i.v. medium dose methotrexate and prolonged administration of intrathecal triple therapy). Total duration of treatment: 116 weeks. 190 patients were enrolled in the study. At 10 years, the EFS rate for all patients is 81.5 +/- 2.8%, the survival rate 84.8 +/- 2.7%, and the cumulative incidence of isolated CNS relapse 1.1 +/- 0.8%. The 10-year survival rate for the 139/190 (73.1%) patients with standard risk non-T lineage ALL according to the NCI risk criteria is 80.5 +/- 3.4%. DCLSG protocol-7 was identical to the intensive ALL-BFM-86 protocol, but cranial irradiation was restricted to patients with initial CNS involvement. Patients were stratified into three risk groups (SRG, RG and EG). Treatment duration was 18 months. 218 patients were enrolled in the study. At 10 years, the EFS rate for all patients is 63.4 +/- 3.3%, the survival rate 76.4 +/- 3.0%, the 5-year cumulative incidence of isolated CNS relapse 5.7 +/- 1.8%. The EFS rate at 10 years of the 127/218 (58.3%) patients with standard risk non-T-lineage ALL according to the NCI risk criteria was 67.9 +/- 4.3%, which is not significantly different from the results achieved in this category of patients with the moderately intensive treatment according to protocol ALL-6 (logrank P = 0.17). These DCLSG studies indicate that omission of cranial irradiation does not jeopardize the overall good results.