THE ESOPHAGUS is exceptionally sensitive to the erosive effects of acid gastric juice. 1 It seems clear that an anatomically poorly defined but physiologically competent sphincter located between the esophagus and stomach must prevent reflux of acid gastric juice into the esophagus. Destruction of this sphincter by incision or excision produces reflux; these experimental observations are supported by clinical experience. The aim of this study was to produce an experimental preparation simulating reflux esophagitis in man and to test the value of the fundic fold operation in ameliorating established reflux esophagitis. Methods and Materials Operative Procedure. —Twenty-four mongrel dogs weighing 14 to 20 kg were anesthetized with sodium pentobarbital. A cuffed endotracheal tube was inserted and attached to a Harvard type respirator. The left chest was prepared and the pleural cavity entered through the eighth intercostal space. The esophageal hiatal ring was incised and the stomach mobilized. After mobilization of