Background: We aimed to determine the incidence and causative factors of reflux esophagitis following Helicobacter pylori eradication in Japanese patients. Methods: In patients in whom reflux esophagitis could not be detected endoscopically,we conducted an annual follow-up observation in 326 H. pylori-cured patients, 199 H. pylori-positive patients, and 151 H. pylori-negative patients, to study the incidence and causative factors of reflux esophagitis. Results: Development of reflux esophagitis was observed in 74 (22.7%) of the H. pylori-cured patients during a median follow-up period of 6.0 years, in 16 (8.0%) of the H. pylori-positive patients during a median follow-up period of 5.0 years, and in 29 (19.2%) of the H. pylori-negative patients during a median follow-up period of 5.4 years. The results, after correction for sex and age, showed that H. pylori-cured patients had a significantly higher risk of reflux esophagitis than H. pylori-positive patients (risk ratio, 2.43; P< 0.01), but their risk did not differ from that in the H. pylori-negative patients. It was also shown that hiatal hernia (risk ratio, 4.01; P< 0.01) and smoking history (risk ratio, 1.77; P< 0.05) were significant risk factors for the development of reflux esophagitis. Conclusions: With regard to the development of reflux esophagitis following H. pylori eradiation therapy, we observed that the frequency was higher in H. pylori-cured patients than in H. pylori-positive patients, but the frequency in H. pylori-cured patients and H. pylori-negative patients was the same. We elucidated that hiatal hernia and smoking history are important risk factors for reflux esophagitis. Background: We aimed to determine the incidence and causative factors of reflux esophagitis following Helicobacter pylori eradication in Japanese patients. Methods: In patients in whom reflux esophagitis could not be detected endoscopically, we conducted an annual follow-up observation in 326 H. pylori- cured patients, 199 H. pylori-positive patients, and 151 H. pylori-negative patients, to study the incidence and causative factors of reflux esophagitis. Results: Development of reflux esophagitis was observed in 74 (22.7%) of the H. pylori -cured patients during a median follow-up period of 6.0 years, in 16 (8.0%) of the H. pylori-positive patients during a median follow-up period of 5.0 years, and in 29 (19.2%) of the H. The results, after correction for sex and age, showed that H. pylori-cured patients had a significantly higher risk of reflux esophagitis than H. pylori-positive patients (risk ratio, 2.43; P <0.01), but their risk did not differ from that in the H. pylori-negative patients. It was also shown that hiatal hernia (risk ratio, 4.01; P <0.01) and smoking history (risk ratio, 1.77; P <0.05) were significant risk Factors for the development of reflux esophagitis. Conclusions: With regard to the development of reflux esophagitis following H. pylori eradiation therapy, we observed that the frequency was higher in H. pylori-cured patients than in H. pylori-positive patients, but the frequency in H. pylori-cured patients and H. pylori-negative patients was the same. We elucidated that hiatal hernia and smoking history are important risk factors for reflux esophagitis.