We prospectively investigated the association between gastric cancer screening and subsequent risk of gastric cancer in a large-scale population-based prospective cohort study, with a 13-year follow-up in Japan. Data were analyzed from a population-based cohort of 42,150 (20,326 men and 21,824 women) subjects. Approximately 36% of subjects reported that they had undergone screening photofluorography during the preceding 12 months, and were regarded as the screened group. A total of 179 gastric cancer deaths and 636 incident gastric cancers were identified during the follow-up period. We observed a 2-fold decrease in gastric cancer mortality in screenedversusunscreened subjects (RR = 0.52; 95% CI = 0.36–0.74). The extent of the reduction in mortality for gastric cancer was greater than in death from all causes excluding gastric cancer (RR = 0.71; 95% CI = 0.65–0.78). A significant decrease in the incidence of advanced gastric cancer was observed in screened subjects (RR = 0.75; 95% CI = 0.58–0.96), although the overall incidence rate did not differ significantly between the screened and unscreened subjects (RR = 1.06; 95% CI = 0.90–1.25). In age-stratified analyses, a significant reduction in gastric cancer mortality was seen in screened subjects aged 40–49 years at baseline, compared with a lesser reduction in screened subjects aged 50–59 (RR = 0.30, 95% CI = 0.13–0.72; and RR = 0.60, 95% CI = 0.40–0.88, respectively). These findings suggest that gastric cancer screening may be associated with a reduced risk of mortality from gastric cancer.