Mass screening for gastric cancer in Japan has been conducted nationwide since 1960. The total number of examinees in 1985 amounted to 5,161,876 and 6,240 cases (0.12%) of gastric cancer were detected. Approximately half of these cases were early stage cancers. According to the studies of mass gastric screening in the Miyagi Prefecture, Japan, the sensitivity of the screening test by the indirect x-ray method was 82.4%, and the specificity was 77.2%. The positive predictive value was 1.78%. Recently, mortality from gastric cancer has been decreasing in Japan. Many studies have been carried out to investigate the relationship between the decreasing trend of mortality from cancer of the stomach and the effectiveness of mass gastric screening. From these studies and from time trend analyses of incidence and death rates, case-control studies, nonexperimental cohort studies, etc., it is believed that mass screening for gastric cancer is effective in reducing the death rate from cancer at this site.