Twelve patients with ureteral injuries from stab or gunshot wounds were evaluated. All 12 underwent surgical exploration on admission. None of the injuries were diagnosed preoperatively. Eleven of 12 injuries were diagnosed during surgical exploration. Diagnosis was delayed in one patient, until 2 weeks after injury, when a CT scan revealed a urinoma. High-dose intravenous urograms (IVUs) were nondiagnostic in nine of nine patients. Hematuria was absent in 45% of patients (5 of 11). Repair of ureteral injury was successfully performed on the proximal and middle portions of the ureter (nine patients) with stented ureteroureterostomy. Three patients sustained distal ureteral injuries. Two underwent ureteroneocystostomy and psoas hitch, and one a primary repair. Mean follow-up time after repair was 4 months in nine patients, and only two minor complications were noted. Currently available preoperative methods, including urinalysis and high-dose IVU, are not reliable for detecting penetrating ureteral injury. In addition, 1 of 12 ureteral injuries was not initially identified, despite routine surgical exploration, urinalysis, and high-dose IVU. A high index of suspicion is required to diagnose ureteral injury.