We evaluated the myoelectrical and motor function of the esophagus, small intestine, colon and anal sphincter in four patients with chronic idiopathic intestinal pseudo-obstruction. All patients had aperistalsis of the esophagus, with incomplete relaxation of the lower esophageal sphincter after swallowing or balloon distension. Duodenal slow-wave frequency was normal at 11.4+/-0.3 (+/-S.E.M.) cycles per minute. The patients did not have a normal increase in duodenal spike or motor activity after intestinal distension, but duodenal activity increased after stimulation with intravenous secretin. Colonic slow-wave activities were present at two frequencies, 6.2+/-0.3 and 3.3+/-0.1 cycles per minute. Neostigmine administration increased both colonic spike and motor activity normally. These studies suggest that in this disorder, physiologic neural responses to swallowing or intestinal distension are impaired but the intestinal smooth-muscle slow-wave activity and the spike and motor responses to exogenous neurohormonal stimulation are intact.