The spread of H. pylori started from the African continent 58,000 years ago, with changes in its virulence during the great spread of ancient humans throughout the world. Unfortunately, carcinogenic risk is high in association with the East Asia strain, which is the main strain isolated in Japan. After the Japanese government health insurance approved eradication therapy in 2000, the incidence of peptic ulcers clearly decreased. Moreover, the incidence of gastric cancer is expected to decrease about one-third by eradication, and its effect is profound among the young whose atrophic change in the gastric mucosa is mild. In other words, the risk of gastric cancer does not reach zero, but still persists. Therefore, periodic upper GI endoscopy should be performed every 1 to 2 years to diagnose gastric cancer, which could develop after eradication.<br>The term “chronic gastritis” was originally defined as “morphological gastritis” such as mucosal inflammation. However, conventionally, patients suffering from epigastralgia and/or dysmotility have been diagnosed with “chronic gastritis” in the Japanese language. That is, two different conditions of “morphological gastritis” and “symptomatic gastritis” are expressed using the same term of “chronic gastritis”. Patients with “chronic gastritis” expect to be treated for certain symptoms, so the meaning of “chronic gastritis” here is “symptomatic gastritis”. Patients have less concern about treatment when suffering from “morphological gastritis”, so only doctors are concerned with this “morphological gastritis” in the case of treatment of “chronic gastritis”. In this way, both doctors and patients have been confused about the term “chronic gastritis” in clinical practice in Japan. Finally, “symptomatic gastritis” is independent of these and clearly defined as functional dyspepsia (FD) in Japanese clinical practice in 2013.<br>FD is known as a multifactorial disease. Many kinds of treatment strategy for it have been studied. H. pylori has a few but clear effects on the pathogenesis of FD. Indeed, for every 13 patients in which it is eradicated, only 1 patient can be cured. However, many physicians feel that the symptoms of many more FD patients are relieved by eradication therapy in clinical practice. To explain this phenomenon, the placebo effect has an important role. From the results of a systematic review, placebo eradication therapy provided a high placebo effect of more than 50%. Therefore, many patients who undertook eradication therapy might improve symptoms via the placebo effect. We should keep this in mind when dealing with FD.<br>There are 3 reasons for the significance of eradication therapy for FD patients. First, H. pylori is the cause of a certain percentage of cases; second, eradication results in the prevention of gastric cancer, which is the most significant effect of eradication therapy; and third, adverse effects by eradication therapy are generally mild and acceptable. From these points of view, eradication should be the first option in patients with H. pylori-positive FD.<br>Since the prevalence of H. pylori-negative gastric cancer (which means not post-eradication, but never infected) is reported to be very low, at less than 1% among gastric cancer cases, infection control should be the most important factor to eradicate gastric cancer from Japan. H. pylori infection occurs from infancy to childhood, so infection control during these periods should be important. When parents are infected, their children would be infected by them. Regrettably, parents become infectious sources for their own children. Therefore, ideally, eradication of H.<br>(View PDF for the rest of the abstract.)