Achalasia is characterized by an intrinsic denervation of the esophagus. It is not known whether this process extends to other parts of the gastrointestinal tract. By means of the modified sham feeding test, we studied the innervation of the stomach and the pancreas in 13 patients with achalasia. We compared the results with those from a group of 15 healthy controls and a group of 10 vagotomized patients. We saw two patterns of response in the achalasia group: 6 patients secreted acid and released pancreatic polypeptide, as did the controls. The other 7 patients neither secreted acid nor released pancreatic polypeptide after modified sham feeding, as did the vagotomized patients. We conclude that some patients with achalasia have denervation of the stomach and pancreas, as assessed by the modified sham feeding test. These differences are unrelated to age, sex, and duration and severity of the disease or treatment. Interestingly, all patients who responded normally developed reflux esophagitis after dilatation. Besides being an interesting pathophysiologic observation, the response to modified sham feeding can help identify those patients at greater risk of developing reflux esophagitis after esophageal dilatation.