Cost-effectiveness analysis of gastric cancer screening in Japan was performed, and the cost-effectiveness ratio was compared with that of colorectal cancer screening. The analytical model was the same as that adopted in our previous study on colorectal cancer screening (Tsuji et al. 1991). The results indicated that the cost per case-fatality prevented by colorectal cancer screening was 5.5 and 2.7 times more expensive for males and females, respectively, than that by gastric cancer screening. The age of the population influenced the cost-effectiveness of screening programs. The cost-effectiveness ratio in gastric cancer screening became negative among males older than the age of 65 years, suggesting that the total cost for prevention and control of deaths by gastric cancer in these age populations is saved by the screening program.