During the last 6 years 73 previously untreated children and adolescents with acute lymphoblastic leukemia were enrolled on a non-randomized therapy protocol. In this longitudinal sutdy the specific accent was put on the intensified induction treatment of 8 weeks' duration which was thought to achieve a higher remission quality. In this phase 8 effective drugs were applied up to the patient's tolerance limits; in addition prophylactic irradiation to the central nervous system was given in two modifications. After 4 weeks all patients were in complete remission. During the first 4 months 6 children died due to complications for which therapy must be at least partially responsible. 17 out of 67 patients relapsed between 4 and 59 months after diagnosis, which corresponds to a remission rate according to the life table analysis of 62% (50 out of 67 patients in first remission). The majority of patients with relapse is characterized at diagnosis by a specific pattern of clinical findings. 2 therapy groups, differently treated in respect to central nervous system irradaiation and duration of continuation therapy, do not at present statistically differ from each other. According to statistics 8 more children may be expected to suffer from relapse. The improved results are due to a lower incidence of bone marrow relapses; it seems that there is a direct relation between intensity of treatment during the induction phase and the occurrence of bone marrow relapses. The specific problems of the presented study take place during the induction phase, which, due to toxicity, regularly results in a number of side effects and severe complications. In order to realize the induction therapy, the use of prophylactic and supportive procedures is of utmost importance. Profound knowledge of possible side effects and complications is most essential as well as the knowledge of how to cope with these problems. It is the authors' opinion that the induction phase can only be performed in specialized institutions, because only at these places enough information may be obtained from an adequate number of patients and only there pediatric oncologists may share in the decisions and responsibilities. Only by using every kind of medical service this method of therapy may be justified at present, according to the results of this study, for the benefit of children with leukemia.