The variability in the published results for colonoscopy and barium enema examinations is confusing. With both, optimum studies depend on meticulous preparation, technical excellence, and operator proficiency. The equivalency of results and the lower cost of the radiologic study indicate that the double-contrast barium enema is the technique of choice for the examination of asymptomatic patients or symptomatic individuals without known antecedent disease. The relatively small difference between the cost of the double-contrast enema examination and sigmoidoscopy ($193 versus $135) suggests that it should replace the latter on the 3-5-year screening schedule because, on average, 50% more of the colon is examined by the barium study. It is a mistake to place colonoscopy and barium enema in competitive positions; the two methods ideally complement one another. The exclusion of significant pathologic findings by the double-contrast enema can be accepted, but the detection of abnormalities should be followed, when necessary, by colonoscopic verification and/or biopsy. The number of times both will be required are few. Radiologically demonstrated colon carcinomas seldom require biopsy verification, and 90% of all polyps are smaller than 5 mm in diameter with a negligible incidence of malignant transformation. When the examinations are used in the proper sequence, they provide a cost-effective approach to the early detection and control of cancer of the large bowel.