Thirty one patients with GI bleeding of obscure origin, defined as those with normal upper endoscopy and colonoscopy, were studied to know the yield of different diagnostic procedures. Seventeen patients consulted for hematochezia and bleeding less than 10 days of evolution in 71%. Small bowel X ray examination was performed in 14 cases with a diagnostic effectiveness (number of diagnosis/number or examination) of 14%, angiography was performed in 12 cases with an effectiveness 33%, radiolabeled erythrocyte scanning in 12 cases with an effectiveness of 75%, scintigraphy with pertechnetate in 6 cases with an effectiveness of 17% and intraoperatory endoscopy in 2 cases with an effectiveness of 50%. A definitive diagnosis was reached in 8 patients during the first admission and in 6 during the second admission. The principal etiologies were small bowel tumors in 3 cases, cecal ulcers in 2 and ileal diverticula in 2. Ten subjects were subjected to surgical and 2 to endoscopic treatment. Five patients with recurrent bleeding remain without diagnosis. It is concluded that radiolabeled erythrocyte scanning and angiography are effective examinations that should follow upper and lower endoscopies in the diagnosis of a concealed GI bleeding. When a diagnosis is not reached in the first admission, patients should be following with repeated diagnostic procedures.