Gastric cancer remains among the leading types of cancer worldwide. There is now convincing evidence linking H. pylori to adenocarcinomas of the gastric antrum, body, and fundus. These tumors are rapidly decreasing in incidence in the United States, whereas cardia tumors, tumors unassociated with H. pylori infection, are on the increase. Although criteria for causality have not been completely fulfilled for H. pylori and adenocarcinoma, there are plausible mechanisms by which chronic inflammation could induce carcinogenesis ("mitosis causes mutagenesis"). Because gastric cancer is unusual in the United States, screening and treatment of H. pylori in the general population are unwarranted. Chemoprevention in high-risk populations, however, could potentially be used to decrease risk for adenocarcinomas distal to the cardia.