Surgical interventions on the abdominal, pelvic and retroperitoneal organs are frequently complicated by damage or alteration of the ureter. To prevent intraoperative damage of the ureter the authors suggest a method of visual identification of the ureter by luminescence analysis. A 10% solution of natrium fluorescein (14-20 mg/kg) was used as the fluorochrome. After experimental validation the method was used successfully in 12 patients.