Imaging techniques in the diagnosis of carcinoma of the colon. The variability in the published results for colonoscopy and barium enema examinations is confusing. With both, optimum results are dependent on meticulous preparation, technical excellence, and operator proficiency. It is a mistake to place colonoscopy and the barium enema in competitive positions; the two methods ideally complement one another in the evaluation of high risk individuals, including those with positive Hemoccult tests. The exclusion of significant pathology by the double-contrast enema can be relied on and is less costly to the patient. Detection of abnormalities by a barium enema should, when necessary, be followed by colonoscopic verification and/or biopsy. When used in this sequence, the procedures provide a cost-effective approach to the early detection and control of cancer; it is estimated that observance of the ACS guidelines can reduce mortality rates by 30%. 