The effect of domperidone, a peripheral antidopaminergic drug, on sigmoid motor activity in the irritable bowel syndrome, has been evaluated by measuring pressures in 3 opentipped tubes perfused with distilled water at a constant flow rate of 0.636 ml/min and inserted into the sigmoid colon. Domperidone 20 mg i.v. in 10 patients, did not induce any significant change in basal motility, but prevented the increase in motor activity produced by the infusion of dopamine 5 micrograms/kg/min for 10 min. It appears that domperidone had no effect on sigmoid motor activity, although the inhibition of dopamine-induced motility confirms the presence of specific dopaminergic receptors in the colon and the antidopaminergic action of domperidone.