We studied 5 healthy volunteers and 9 patients with irritable bowel syndrome (IBS) during infusion of the colon with saline solution, bile acids, fatty acids and balloon distension. Our results show that the pain threshold was significantly (p less than 0.001) higher in controls than in IBS patients. Bile acids and fatty acids brought on the habitual pain in 5/7 and 7/8 patients respectively, while they did not have any effect in the control group. On the basis of our data we can conclude that the IBS patients are more sensitive to colonic distension and perfusions, thus suggesting a non-specific irritability of the colon which could be a characteristic of these patients.