Role of in virulence of .

() is a gastric human pathogen associated with acute and chronic gastritis, 70% of all gastric ulcers, 85% of all duodenal ulcers, and both forms of stomach cancer, mucosal-associated lymphoid tissue (MALT) lymphoma and adenocarcinoma. Recently, attention has focused on possible relationship between presence of certain virulence factor and -associated diseases. Some contradictory data between this bacterium and related disorders has been observed since not all the colonized individuals develop to severe disease. The reported diseases plausibility related to specific virulence factors became an interesting story about this organism. Although a number of putative virulence factors have been identified including cytotoxin-associated gene a () and , there are conflicting data about their actual participation as specific risk factor for -related diseases. Duodenal ulcer promoting gene a () is a virulence factor of that is highly associated with duodenal ulcer development and reduced risk of gastric cancer. The prevalence of in strains isolated from western countries is relatively higher than in strains from Asian countries. Current confusing epidemiological reports will continue unless future sophisticated and molecular studies provide data on functional and complete cluster in infected individuals. This paper elucidates available knowledge concerning role of in virulence of after a decade of its discovery.