Introduction: Helicobacter pylori is a Gramnegative, microaerophilic bacterium that colonizes human gastric mucosa. Gastric ulcer, duodenal ulcer, chronic atrophic gastritis, mucosa associated lymphoid tissue lymphoma, and stomach adenocarcinoma are associated with H. pylori as the etiological agent. Cytotoxin associated gene A (cagA), which is one of the most important virulence factors of H. pylori, encodes a 120145 kDa protein. The prevalence of cagA genes shows differences in H. pylori infections based on geographical area, and cagA positive H. pylori strains play an important role in pathogenesis of gastric carcinoma.