BACKGROUND & AIMS: We have shown previously that cure of Helicobacter pylori infection leads to the disappearance of acid-neutralizing substances. Also, patients with ulcer after cure may gain weight. The aim of this study was to investigate whether cure of the infection increases the risk of reflux esophagitis. METHODS: Patients with duodenal ulcer without reflux esophagitis at the time of Helicobacter treatment were followed up prospectively after cure of the infection (n = 244) or after diagnosis of persisting infection (n = 216). All patients underwent endoscopy at 1-year intervals or when upper gastrointestinal symptoms recurred. H. pylori infection was assessed by rapid urease test and histology. RESULTS: The estimated incidence of reflux esophagitis within 3 years was 25.8% after cure of the infection and 12.9% when the infection was ongoing (P < 0.001). Patients who developed reflux esophagitis after the cure had a more severe body gastritis before cure (odds ratio, 5.5; 95% confidence interval [CI], 2.8-13.6), gained weight more frequently after cure (odds ratio, 3.2; 95% CI, 1.2-9.4), and were predominantly men (odds ratio, 3.6; 95% CI, 1.1-10.6). CONCLUSIONS: A considerable proportion of patients with duodenal ulcer treated for H. pylori will develop reflux esophagitis; risk factors are male sex, severity of corpus gastritis, and weight gain. (Gastroenterology 1997 May;112(5):1442-7)