Almost all patients infected with Helicobacter pylori develop chronic active gastritis, and some progress to atrophic gastritis, intestinal metaplasia, and eventually gastric cancer via Correa’s cascade. H. pylori is also the causative agent for peptic ulcers and mucosal-associated lymphoid tissue lymphoma, as well as extra-gastric diseases such as idiopathic thrombocytopenic purpura. Primary prevention via the elimination of the etiological factor is a promising strategy to reduce the incidence of gastric cancer. The best means of reducing or eliminating gastric cancer is the prevention of H. pylori infection or the treatment of H. pylori before the development of atrophic gastritis. Theoretically, the elimination of H. pylori infection at an early age when individuals are healthy or only have mild gastritis will eliminate about 89% of gastric cancers. However, in reality, subjects undergo screening at diverse ages, and a meta-analysis showed that eradication of H. pylori infection was associated with a 47% reduction in the risk of gastric cancer. Importantly, even for patients diagnosed with early gastric cancer who underwent endoscopic mucosal resection, H. pylori eradication still showed a significant reduction in the risk of metachronous gastric cancer, which suggests that the eradication of H. pylori is important even at the late stage. Therefore, the current consensus is that eradication of H. pylori prevents gastric cancer. Our attention is now focused on how the eradication of H. pylori can be achieved on the total population level. Several consensus meetings have emphasized the importance of applying the “population-based screen-and-treat” strategy to decrease the burden resulting from a high prevalence of gastric cancer. In this talk, I will discuss about the impact of H. pylori eradication on human health both in high-income countries (e.g., Japan) and low- and middle-income countries (e.g., Bhutan).