To determine the utility of pre-operative abdominal computerized tomography (CT) scanning in patients with colorectal cancer, a prospective analysis was undertaken of all patients referred to a colorectal clinic for the primary treatment of colorectal cancer in a 5-year period. A clinical decision regarding the type of surgery to be performed was made prior to CT scanning, and this was then compared with the final surgery performed for each patient. The reason for any change in management was noted. Definitive management differed from proposed management in 14 of 116 patients studied. Surgery was avoided in one patient found to have multiple liver metastases on the CT scan. Operative findings changed the management in the remaining 13 patients. Seven patients had less aggressive surgery than proposed, one patient's surgery was abandoned because of extensive disease, and five patients had more radical surgery. Routine pre-operative CT scanning of the abdomen in patients with colorectal cancer does not seem to be justified from the results of this study.