The diagnosis of lower intestinal hemorrhage usually follows the successive sequence: a) digital rectal examination, b) rectosigmoidoscopy, c) barium enema, d) colonoscopy. This latter method has proven to be the most sensitive. This study is a retrospective examination of the results obtained by emergency colonoscopy on the diagnosis and treatment of lower intestinal hemorrhage. Out of 1258 colonoscopy procedures performed between January 1983 and June 1988 in the Digestive Endoscopy Unit of our Institute, 44 (3.5%) were emergency procedures (within 48 hrs. after recovery) due to lower intestinal hemorrhage. The most frequent causes of hemorrhage found were the following: 1) hemorrhagic colitis (20.5%), 2) polyps (13.6%), 3) hemorrhoids (13.6%), 4) carcinoma (9.0%). The hemorrhagic source was not established in 9 cases (20.5%). The sensitivity of this method was therefore 97.2%. In 6 cases of hemorrhagic polyps treatment to stop bleeding was also possible by means of the colonoscopy (endoscopic polypectomy). In our experience, the emergency colonoscopy was found to be a highly sensitive diagnostic procedure for lower intestinal hemorrhages, permitting even definitive treatment of the lesion in 13.6% of cases with no complications associated with the technique. We feel therefore that, when available, it should be considered the first and foremost exam to be performed for emergency diagnosis of colo-rectal hemorrhages.