We compared the use of barium enema (BE) and colonoscopy in evaluating patients with chronic gastrointestinal tract bleeding by dividing into three groups 329 consecutive colonoscopies and 207 consecutive BE examinations done with chronic gastrointestinal tract bleeding as an indication. In the first group, of 96 patients with negative results of BE studies, subsequent colonoscopy showed carcinoma of the colon in 16%, polyps larger than 1 cm in 21%, and other causes in 20%. In 43% the colonoscopy gave negative results or was incomplete. In the other two groups we directly compared findings of the 207 BE and the 233 remaining colonoscopies when each was used as a primary diagnostic test. Colonoscopy was found to have fewer negative results (74% vs 43%), fewer inconclusive examinations requiring repeat (19% vs 3%), and more positive correct findings to explain the cause of bleeding (54% vs 5%).