We have reported that prevalence of H. pylori infection and grade of atrophic gastritis were significantly lower, while acid secretion was significantly greater in the patients with reflux esophagitis than those without it. We have also reported that increased gastric acid secretion after H. pylori eradication may explain a reason for developing reflux esophagitis. Therefore, H. pylori is considered to be a protective factor for the development of reflux esophagitis via the induction of gastric hyposecretion. Conversely, according to recent large population-based studies, no evidence was obtained that supports the increased frequency of heartburn symptoms or reflux oesophagitis after the eradication of H. pylori. One reason for the discrepancy may be the difference in the evaluation of gastro-esophageal reflux, another reason may be the difference in acid secretion before the clearance of H. pylori in individual subjects, because the effects of H. pylori on acid secretion vary from patient to patient.