This chapter discusses the role of Helicobacter pyiori in gastric cancer. The discovery of H. pylori infection ranks as one of the most important medical discoveries of the 20 th century. The impact of H. pylori infection is in the treatment of peptic ulcer disease; epidemiologic studies show that H. pylori are the most important single factor responsible for gastric cancer. The recognition of H. Pylori, as a key risk factor for gastric cancer, contributes to the understanding of gastric carcinogenesis and also offers the prospect of preventing this lethal disease through the elimination of the infection. The eradication of H. pylori infection leads to resolution of inflammation, elimination of DNA damage by ROS, reduction in cell turnover, increase in acid output, and ascorbic acid secretion into gastric juice. To determine the logical measure to prevent gastric cancer development of H. pylori eradication, much more evidence needs to be collected, including the variation of virulence factors in the bacteria, host responses to inflammation, and side effects after eradication.
