Hyperventilation is associated with some symptoms suggestive of irritable bowel syndrome and has been implicated in provoking excessive oesophageal contractility. Sixteen patients with irritable bowel syndrome were therefore studied in order to assess the effect of hyperventilation on distal colonic motility and rectal sensitivity. No significant change in either the amplitude or frequency of colonic contractile activity was noted following hyperventilation, nor was any alteration in rectal sensitivity observed. This study shows that acute hyperventilation does not affect colonic motor activity or visceral sensitivity and suggests that hyperventilation and irritable bowel syndrome are not causally related.