COLUMNAR epithelium completely lining the lower esophagus in man was described by Barrett1 in 1950. The clinical importance of heterotopic gastric mucosa, whether in Meckel's diverticulum or the esophagus, has been well documented. This occurrence in the esophagus in relation to the origin of acid-peptic esophagitis, stenosing acid-peptic esophageal stricture, and peptic ulcer of the esophagus has been widely discussed. The origin of gastric heterotopic mucosa in the esophagus remains unsettled. For this reason, the effect of gastroesophageal reflux upon regeneration of esophageal mucosal defects and sphincter incompetence was studied. Method Nine mongrel dogs of either sex weighing 9 to 11 kg (20 to 24 lb) were anesthetized with 28 mg/kg of sodium pentobarbital for veterinary use only (Diabutal). Each dog was placed on the operating table on its right side. An endotracheal tube, connected to a positive pressure respirator using ambient air, insured adequate ventilation during the procedure.