Progress in techniques of diagnosing gastric cancer has made it possible to detect small lesions. Because of this advance, mass screenings for gastric cancer have been encouraged. Early gastric cancers have reached more than 30% of all gastric cancers at many hospitals in Japan. However, more than 50% of patients with gastric cancer have advanced cases. To detect early gastric cancer and to treat advanced cancer are both important clinically. This paper reviews studies of special interest in these areas.