Acid related diseases in Japan has changed during the past 50 years. Previously the prevalence of peptic ulcer, especially gastric ulcer was the most common acid related disease, and now reflux esophagitis is the most common diasease. Among peptic ulcer disease, the prevalence of drug-induced bleeding peptic ulcer is increasing. On the other hand, the prevalence of atrophic gastritis and gastric cancer is decreasing, because the infection rate of Helicobacter pylori had been decreasing, the eradication therapy for Helicobacter pylori is now popular, and the lifestyle has westernized. In the western countries, the same changes have happened during the long history.