A retrospective study was performed to compare the diagnostic accuracy of high-quality double-contrast barium enema (DCBE) against gold standard colonoscopy in 288 patients with suspected lower gastrointestinal bleeding who went through both examinations. Colonoscopy detected the potential cause of bleeding in 99 patients (100%); in order of frequency: polyps greater than or equal to 1 cm (N = 47; 48%), carcinoma (N = 21; 21%), inflammatory bowel disease (IBD) (N = 15; 15%), solitary ulcers (N = 6; 6%), other types of colitis (N = 5; 5%), angiodysplasia (N = 3; 3%), and stenosis (N = 2; 2%). DCBE diagnosed 88 cases (89%) and missed 11 consisting of IBD (N = 4), angiodysplasia (N = 3), solitary ulcers (N = 3), and polyps (N = 1). The overall sensitivity and specificity of DCBE was 0.89 and 0.97, respectively. The sensitivity for carcinoma, polyps, and IBD was 1.00, 0.98, and 0.73, respectively. We conclude that DCBE is very effective to diagnose carcinoma and polyps greater than or equal to 1 cm, the most frequent causes of bleeding, but less effective to diagnose IBD and other nonfrequent causes. If a high-quality DCBE does not reveal the cause of bleeding, the contribution of a following colonoscopy will be to diagnose causes of bleeding other than carcinoma and polyps less than 1 cm and to offer therapeutic possibilities.