We retrospectively studied intravenous urograms (IVU) performed at presentation on 108 children with acute leukemia in order to determine whether any association existed between an abnormal IVU and known prognostic factors at presentation, initial renal function, and outcome. Sixteen patients (14%) had abnormal IVUs. These patients were compared to the remainder of the group and found to be comparable in respect to known prognostic factors at diagnosis (P greater than 0.05). No correlation was found between abnormal renal function and an abnormal IVU. Renal enlargement was associated with shorter survival only in patients who had both adenopathy and hepatosplenomegaly (P less than 0.01). This effect did not persist in any other group of patients examined. When subjected to multivariate analysis the IVU did not significantly influence relapse or survival in these patients. Renal enlargement may be a prognostic feature in some patients with childhood leukemia. Nevertheless routine evaluation by IVU is discouraged because of potential adverse affects of urographic contrast media and the availability of noninvasive ultrasound techniques.