Abdominal spiral computed tomography (CT) pneumocolon is performed after cleansing the colon, using a smooth muscle relaxant and rectal air insufflation. Rapid dynamic scanning is undertaken with intravenous contrast to give optimal hepatic and vascular enhancement, and 5-10 mm contiguous slices. The area of interest in the colon is reconstructed every 2.5 mm. This technique was performed in four patients with colorectal cancer and the CT findings were compared with the barium enema and pathology following surgical resection. Spiral CT pneumocolon clearly showed the primary tumour in all cases as an enhancing soft tissue mass, and was able to detect local extension and lymphadenopathy as well as assess the liver, peritoneum and remaining abdomen. CT depicted the morphology of the primary tumour more clearly than barium enema, and in one case also detected a 1 cm polyp which was not seen on the barium study because the patient was incontinent of barium and views were limited. There was good correlation between the CT and pathological findings. Compared to a barium enema, spiral CT pneumocolon is quick, with minimal patient discomfort, no risk of barium incontinence, and there is good assessment of the local and distant abdominal disease. Multiplanar formatting is possible and 3-D reconstruction gives intra- and extra-luminal views.