This retrospective study examined ureteral injuries during gynecologic operations from January 1980 to August 1985. The study was conducted at two private hospitals that are involved in resident teaching programs. Each patient was reviewed for predisposing factors, location and type of injury and time and method of recognition. Sixteen injuries were documented in 1,093 extensive procedures. Twelve injuries occurred at the pelvic brim and four others occurred elsewhere in the pelvis. Risk factors included previous surgical procedures in the pelvis, endometriosis, ovarian neoplasm, pelvic adhesions, distorted anatomic features of the pelvis and repair of the bladder. The anatomic structure of the ureter is reviewed, and recommendations are made to help prevent ureteral injury during surgical procedures in the pelvis.