Aim: Ingestion of a meal frequently induces an urge to defecate, the so-called gastro-colonic or gastro-rectal reflex. In patients with irritable bowel syndrome (IBS), symptoms are often provoked by meals. CCK, a proximal gut peptide released after meal ingestion, may mediate these postprandial changes. The potential role of CCK in rectal sensory and motor function was evaluated by rectal barostat study in healthy controls and patients with IBS. Method: The sensory effects on serosal and mucosal receptors were studied. Twelve healthy controls and 12 patients with IBS underwent a ramp distension procedure of the rectum during infusion of CCK and placebo in random order. In 10 other healthy controls and 10 IBS patients an intermittent distension procedure was performed during infusion of CCK and placebo in random order. Results: No differences were found in rectal compliance during ramp distensions between IBS patients and controls. CCK did not affect perception of urge and pain, in controls or in IBS patients. Similar results were obtained during the intermittent distensions, but at higher distension pressures CCK significantly increased rectal sensitivity in IBS patients. Conclusion: Infusion of exogenous CCK to plasma levels normally seen in the postprandial state, did not influence rectal motor function or sensations during ramp distension but it did significantly increase pain sensation in IBS patients during rapid intermittent distension. (c) 2012 The Authors Colorectal Disease (c) 2012 The Association of Coloproctology of Great Britain and Ireland.