The treatment of childhood leukemia in Hungary is carried out in the framework of a national multicenter study. During the past ten years 633 newly diagnosed patients were treated in one of the ten centers. Of these, 39 were less than a year old at the time of diagnosis; 24 presented with ALL, 12 with AML, and three were found to have juvenile CML. Initial WBC count, which is the most important prognostic factor in childhood leukemia, was significantly higher in infants than in older children. Accordingly, the treatment results in these patients were inferior to those in children. Therapy of leukemia in infants remains a serious problem and warrants further studies to establish the best approach.