In this study, although the prevalence of AG genotype of rs2230724 was not significantly different (52.4% vs. 49.3%, respectively) in the cohort of cases and negative cohort, the ratio of the prevalence of AG and GG (the reference) was significantly different (2.41 in cases vs. 1.64 in controls), which was also indicated by the low P value (P = 0.030) for the adjusted OR, suggesting an important role of JAK2 gene rs2230724 polymorphism in the risk of gastric cancer. The gene discussed is JAK2; the disease is gastric cancer.