Seven hundred fifteen cases of lower digestive tract bleeding were studied by fiber-endoscopy. The causes of bleeding were detected in 489 cases (68.4%) . The major causes were; chronic colitis in 169 cases (23.6%) , ulcerative colitis 91 (12.9%) , colonic polyps 139 (19.4%) and colonic cancer 66 (9.23%) . The minor causes were vascular dilatation, Crohn's disease, diverticulum of colon, pseudopolyposis of colon and amebiasis, etc. For searching the site of lower intestinal bleeding, colonoscopy is superior to barium enema not only for the higher detection rate but also for the direct visualization and verdict through biopsy.