During a 9-month period, 2 590 patients were referred for radiographic examination of the large bowel. All but 55 of these examinations were performed according to the double contrast examination method. The patients were followed prospectively from 40 to 48 months. Carcinoma of the colon or rectum was disclosed in 96 patients and other malignant lesions in 7 others. The carcinomas in 93 patients were diagnosed at the primary DCE. During the follow-up period, carcinoma of the colon was revealed in another 10 patients, the malignancy having been obfuscated by diverticulitis in 3 patients and considered polyps in 6 others. The accuracy of the double contrast method was calculated at 99.3 per cent.