Distal colonic motor activity was measured in 12 control subjects and seven constipation-predominant irritable bowel syndrome patients to examine the effects of intravenous administration of cholecystokinin. In the basal state, no significant motility differences were noted between these two groups. Following the intravenous administration of the hormone cholecystokinin, a statistically significant reduction in colonic motility in control subjects and a non-significant decrease in motility in irritable bowel syndrome patients was seen. Our results do not suggest an exaggeration of the colonic motor response to cholecystokinin occurs in irritable bowel syndrome.