Helicobacter pylori (H. pylori) infection is recognized to be a pathogen of various gastro-duodenal disease. Eradication therapy of H. pylori reduces the recurrence of gastro-duodenal ulcer, improves gastritis histologicaly, and is suggested to act an certain role in protection against gastric carcinogenesis. Although, several studies show uncomfortable results arise after H. pylori infection was cured. These studies suggest that gastro-esophageal reflux disease (GERD) and gastro-doudenal erosion may increase after successful eradication of H. pylori. Recently, adenocarcinoma of the gastric cardia and esophagus increase in incidence. Reflux esophagitis and Barrett's esophagus are recognized as precancerous lesion of esophageal adenocarcinoma. It is uncertain the association of newly occurrence of GERD after H. pylori eradication and increase of esophageal adenocarcinoma. Although GERD may lead to adenocarcinoma, long term observations is necessary after H. pylori eradication.