Frequently traumatic injury to the renal pelvis or upper ureter is overshadowed by multiple associated injuries. The diagnosis may be particularly difficult, due to the lack of hematuria and absence of pathognomonic findings. All too frequently the delayed manifestations of urinary wound drainage, retroperitoneal mass, or urinary ascites and sepsis first draw attention to the ureteral injury. A review of the problem and our experience with 16 such injuries is presented. As with other infrequent injuries the single and most important diagnostic factor is the prepared mind of the examiner. We feel all patients who have penetrating abdominal trauma, have fractured lumbar processes, or are involved in accidents where deceleration or extension occur should have infusion pyelography even in the absence of hematuria.