Information concerning 32 infants with abdominal masses noted during the first day of life is presented. The most common mass was a hypoplastic, multicystic kidney which was the final diagnosis in 13 of 32 cases. The mass proved to be a malignant tumor in four instances (an incidence of 13%). Preoperative intravenous urogram should be made in every instance, even the obvious hydrometrocolpos may present a marked secondary hydronephrosis. In the other cases, one can rarely be certain that the mass is not of renal origin. Of the 30 infants undergoing surgery, there were three deaths, either from the surgery or in the immediate postoperative period—a mortality rate of 10%. The presence of an abdominal mass in the newborn infant, the same as for older patients, constitutes an indication for early surgical intervention. Delay on the basis that the baby is too small or too young cannot be justified.