BACKGROUND: Lower gastrointestinal bleeding is a commun clinical entity. Although colonoscopic examination is the first choice for diagnosis, it may not be enough to reveal the cause of bleeding in all subjects. METHODS: Eight patients who had massive lower gastrointestinal bleeding having normal colonoscopic findings were retrospectively evaluated at the Department of Trauma and Emergency Surgery, Istanbul University, Faculty of Medicine RESULTS: There were 5 male and 3 female patients with mean age of 51 (28 to 82). Patients received a mean of 13 U (range 2 to 23) with transfused erythrocyte concentrates. Four patients had found to be normal during angiographic, scintigraphy or enterocylytic examinations. Angiography was diagnostic in 4 patients, and identified bleeding from ileocolic pseudoaneurisms (n= 2) branches of jejunal artery (n=2). Embolization procedure were performed in these 4 patients and 3 of them developed intestinal necrosis and underwent surgery. One did not require further treatment. Two of the patients who underwent surgery expired due to sepsis. Patients were hospitalized for a mean of 17 days (range 5 to 37). CONCLUSION: Despite employment of all diagnostic procedures, the cause of bleeding were not detected in half of patients who had normal colonoscopic findings. If angiographic treatment is necessary, superselective arterial embolization should be performed.