|Although the incidence and mortality of gastric cancer have recently been declining, it is still a common cancer in Japan. Gastric
cancer remains the fourth most common cancer and the second leading cause of global cancer mortality. Thus, a gastric cancer control
strategy is important in Japan and around the world. Moreover, studies to clarify the etiology of gastric cancer with molecular understanding
are still important work to be done. In this short review, we focus on the etiology of gastric cancer from aspects of oxidative stress. Positive association is presented with
chronic atrophic gastritis, drinking habits, and barbecued or grilled cooking. In addition, Helicobacter pylori (H. pylori) infection is
considered as an important risk factor for gastric cancer. Besides environmental risk factors, genetic factors also play crucial roles in
gastric cancer development. Mutation in the E-cadherin/CDH1 gene resulted in hereditary diffuse gastric cancer. People with Lynch
syndrome, and familial adenomatous polyposis, are high-risk groups of gastric cancer.