Since the development of endoscopy, physicians have been comparing radiographic studies with endoscopic examinations. Colonoscopy and upper endoscopy have largely replaced barium enema and upper gastrointestinal series. Unfortunately, many study protocols comparing colonoscopy with barium enema have been retrospective and the radiologic examination is compared with colonoscopy in a cohort group. The greatest difficulty with interpreting results of these studies is the inclusion of clinically insignificant findings in the calculation of the diagnostic yield. For example, in most studies barium enema is more successful than colonoscopy in diagnosing diverticular disease, and inclusion of this clinically insignificant entity increases the overall yield.