Notwithstanding the extensive study of hydronephrosis in recent years, relatively little has appeared in American and English literature on the congenital type. The condition is not common. In 15,800 admissions to the Robert W. Long Hospital, there were only two cases. Most of the work on hydronephrosis has been related to the early cases of adults, cases which could be detected in their incipiency by modern urologic examination and which afforded the hope of restoring ureteral function and salvaging the kidney. More study of the less hopeful congenital cases may be profitable, because their etiology is not obscured by the scars of many battles with infection, traumatism and indiscretion which individuals of many years of medical history present. DEFINITION OF CONGENITAL HYDRONEPHROSIS In 1885, Morris1 drew a distinction between congenital hydronephrosis and hydronephrosis of congenital origin. He considered the term "congenital hydronephrosis" applicable only to those cases in which