The age-standardized incidence and mortality rates of gastric cancer have been decreasing worldwide. However, due to the rapid increase in the aging population, the absolute number of cases is actually increasing, and some countries, including Korea, show a divergent trend in the incidence of gastric cancer in younger generations. Gastric cancer is the second most common cancer in Korea. In the present review, several epidemiologic factors associated with the risk of gastric cancer are evaluated, including family history of gastric cancer, Helicobacter pylori infection, cigarette smoking, and adverse dietary factors. The practice of and participation in gastric cancer screening are reviewed. Prevention strategies based on evidence from Korean epidemiologic studies and early detection by regular screening are important for the reduction of the burden from gastric cancer.