ANOMALIES of all parts of the body are frequently found, but anomalies in the genito-urinary tract seem to be more frequent than in any other part, with the possible exception of the spine. The roentgenologist, as well as the urologist, must know what anomalies may be found in the genito-urinary tract and, on account of their frequency in this region, constantly have them in mind when interpreting roentgenograms. Nichols says that the pyelographic findings often decide the question as to whether or not surgery is indicated, and that errors are perhaps most frequently due to failure to recognize congenital anomalies of the kidney pelvis. We will not attempt to discuss all of the anomalies of the kidney pelves and ureters, but will speak particularly of the double kidney and duplication of the ureters. Mertz has shown that occasionally the primary division of the pelvis may vary, three or four primary divisions in the ureteral bud may be present, and three or four major calyces result. However, the extreme rarity of further extension of such a division into three or more pelves, with or without three or more separate divisions of the ureter, would seem to indicate that division of the ureteral bud into three or more major calyces would be infrequent. We are not of necessity particularly interested in the embryologic questions as to when or by what means this division takes place. We do not need to decide whether it is a development of separate anlage or whether division occurs from above downward. Whether division takes place from above or below does not concern us, but we should know that division does occur and we should recognize the condition when present. The condition of double kidney, with duplication of the pelvis or partial or complete duplication of the ureter, is, no doubt, frequently present, and is often the seat of disease. This condition is frequently unrecognized, as is indicated by the report of Mertz. He says that many cases are discovered only at autopsy, and that of those diagnosed during life and before operation, the diagnosis was made only after repeated urologic and roentgenologic examinations. The typical normal pelvis of the single kidney has two major calyces, the superior major calyx being long, straight, directed obliquely upward and inward. The inferior is larger, shorter, and more horizontal, and has a tendency toward an oblique downward and lateral direction. The extent of the division between the two major calyces, involving the entire pelvis or including the ureter in varying degrees, results in the bifid pelvis or in the partially or completely duplicated ureter. According to Young the pelves of the double kidney are always situated one above the other, the division being transverse. We believe the division may be longitudinally through the kidney, with one pelvis anterior and one posterior, and in Figure 13 we show what we believe to be such a condition.