Radiologic examinations preceding the diagnosis of colorectal carcinomas were retrospectively scrutinized in 708 patients with 731 carcinomas that were radiographically investigated 741 times. Sixty-four lesions were missed 74 times, giving a 90% sensitivity of the radiographic methods used. Of the errors, 82% were perceptive, and 3% were interpretative. Eleven examinations in nine patients revealed no lesions, although the examinations were done within 2 years of the diagnosis of a carcinoma. Missed lesions were more common than expected in the cecum and the ascending colon (P less than 0.001), and 18% of the patients had multiple tumors (expected incidence 3.6%, P less than 0.001). The median delay in diagnosis was 20 months, and patients whose diagnosis was delayed for a long time tended to have more advanced carcinomas at diagnosis. As a lesion was identified either at the initial examination or retrospectively 730 of 741 times, the potential sensitivity of the radiographic methods used was 99%. It is concluded that barium enema is still an excellent method for the detection of colorectal carcinoma provided that perceptive errors can be minimized.