The Children's Cancer Study Group's (CCG) clinical trials in acute lymphoblastic leukemia (ALL) prior to 1981 consistently demonstrated that patients presenting with a white blood cell count (WBC) greater than or equal to 50,000/microliter or the "lymphoma syndrome" had a less than 40% 3-year event-free survival (EFS). The Berlin Frankfurt Munster (BFM) 76/79 study suggested that the prognosis of these patients could be improved. Before testing this therapy in a randomized setting, 29 CCG institutions used it for treatment of 209 newly diagnosed children with ALL and an initial WBC greater than or equal to 50,000/microliter or the lymphoma syndrome. In the intensive phases of therapy, 77% of cumulative parenteral doses and 55% of cumulative oral doses were within 10% of protocol requirements or were modified appropriately for reported toxicity. One hundred ninety-five patients achieved remission (93.3%). Eleven patients died in remission (5.6%)--10 during the intensive reinduction/reconsolidation phase. The 4-year EFS (+/- 1 SD) was 62% (+/- 3.7%) with a median follow-up of 40 months. Only one patient has had an isolated CNS relapse. These results appear superior to past CCG studies for high-risk patients and extend observations made from studies of similar therapy.