An analysis of the utility of parenteral ceruletide, a cholecystokinin-like synthetic decapeptide, in promoting bowel opacification for computed tomography (CT) scanning was performed. Abdominal and pelvic CT scans of 85 patients who had received intramuscular ceruletide following oral contrast administration and of 85 control patients were reviewed and the degree of bowel opacification evaluated. No significant advantage was conferred by ceruletide in opacifying the stomach or major part of the small intestine. However, a statistically significant difference was found between the 2 groups in the presence or absence of contrast in the terminal ileum and right colon. Contrast was detected in the terminal ileum in 52 experimental compared with 35 control patients (p<0.009) and in the right colon in 56 experimental and 39 control subjects (p<0.01). Intramuscular administration of ceruletide will be helpful when terminal ileal opacification is essential or in patients in whom colonic opacification is desired but rectal contrast contraindicated.