In this retrospective multicentric study, we report on early deaths (ie, those that occurred during the first month of treatment) in a total of 943 newly diagnosed ALL pediatric patients registered from 1976 to 1981 at 21 centers of the AIL- AIEOP . Objectives of this study were as follows: (1) to verify the incidence and the cause of early death in a wide population of children with ALL and (2) to elucidate factors associated with early death and therefore to identify "high-risk" groups of patients. Out of the 943 ALL patients, 39 (4.1%) early deaths were registered. Main causes were infection, 20 patients (51.3%); hemorrhage, 11 patients (28.3%); uric acid nephropathy, 2 patients (5.1%); cardiac failure, 3 patients (7.6%); syndrome of inappropriate antidiuretic hormone secretion, 1 patient. Two patients died during the first week of unknown cause. Thirteen factors measured at diagnosis and possibly influencing the early death rate were analyzed. Using the chi-square test, only three of these factors (age, mediastinum status, surface markers) appear to have any significant influence on the early death rate. We also tried to determine how therapy influences this process by analyzing variations in the early death rate, other factors being equal. Significant differences in the early death rates were encountered in AIEOP protocols using different induction regimens.