Gastric cancer, if diagnosed at the symptomatic stage, has a poor prognosis, with an overall 5 year survival of about 5%. The surgical treatment of early gastric cancer increases this 5-year survival rate to 90%. In Japan, endoscopic surveillance has increased the proportion of gastric cancer detected at an early stage from 15% in 1960 to 50% in 1985, and the overall 5 year survival has been increased from 35% to 70%. Mass screening in Japan is worthwhile because the incidence of gastric cancer is about 80 cases per 100,000 population per annum (age standardized). But in other countries where the incidence is much lower the case for mass screening is weak and selective screening of those at high risk is advocated.