The incidence of colorectal cancer has been gradually going up among the Japanese in the past decade, but a ratio of early cancer is only ten per cent of total lesions. To improve this problem, mass screening in asymptomatic populations will be needed urgently. In order to establish a mass program, it is important to match various factors regarding a disease and method, which makes the screening valuable and acceptable. Fecal occult blood test is the method which will be most acceptable with regard to the cost, time and number to be examined. Since 1979 the author and his colleagues have been evaluating mass screening for colorectal cancer with fecal occult blood testing in combination with gastric mass screening already established in Japan and would like to stress that this combination method is useful and widely acceptable from the viewpoints of cost-benefit and early detection of colorectal cancers. Finally, the author expects that "Gastrointestinal mass screening" with this combination method will be spread throughout the country in the near future.