36 male patients (average age, 36 years) with duodenal ulcer (DU) were studied with the purpose of investigating the incidence of reflux esophagitis. Ten of them had duodenal stenosis due to scarring. All patients were submitted to X-ray and endoscopy of the esophagus, histology of the esophagus, gastric secretion of HCl, and manometry of the lower esophageal sphincter. The results were compared with those of ten controls. The following conclusions were reached: (1) esophagitis according to histological and endoscopic study was found in 61.1% of the patients; (2) the incidence of esophagitis is not significantly related to the duration of the disease, as estimated by its symptoms; (3) duodenal stenosis is not significant in the pathogenesis of the esophagitis; (4) no significant statistical relation was observed between the presence of reflux esophagitis in patients with DU and the gastric secretion of HCl as evaluated in basal conditions and after Histalog stimulation; (5) the length of sphincter and the resting gastroesophageal sphincter pressure were not significantly different in patients with or without esophagitis, and do not depend on the presence or the absence of stenosis or gastric hypersecretion of HCl.