Ceruletide, a decapeptide, is a potent cholecystokinetic agent with a direct spasmogenic effect on the gallbladder muscle and bile ducts in humans and animals. It was recently approved by the Food and Drug Administration for use as an adjunct in x-ray examination of the gallbladder and small bowel. The drug causes a coordinated propulsive activity from the duodenum to the ileum and segmenting activity in the colon. Because of this stimulatory effect, ceruletide is useful not only diagnostically as an aid in x-ray examination of the small bowel, but also therapeutically for treatment of postoperative ileus, intestinal atonia, and chronic fecal statis. Because of its pancreatic stimulatory action, it is useful in evaluation of exocrine pancreatic function. In therapeutic doses the adverse effects noted are mild, transient extensions of the drug's pharmacologic actions and are manifest as nausea, vomiting, abdominal pain, and rarely hypotension and tachycardia. On the basis of current evidence, ceruletide is a safe and effective cholecystokinetic agent and small bowel and exocrine pancreatic stimulant.