Ureteral injuries during the course of surgical procedures within the pelvis occur more frequently than presumed. A series of 65 patients with ureteral injuries is reviewed from the standpoint of pathogenesis, prophylaxis, diagnosis, and treatment. The preferable time for repair of the injured ureter is during operation or early in the period of convalescence. The procedure of choice is end-to-end anastomosis of the severed end of the ureter. In instances in which this cannot be accomplished, the ureter should be reimplanted into the bladder. Preoperative insertion of ureteral catheters as a precaution against ureteral injury is of questionable value.