This paper primarily aimed to overview the rationale for initiating the Japan Collaborative Cohort Study for Evaluation of Cancer Risk Sponsored by Monbusho (Ministry of Education, Science, Sports and Culture of Japan) (JACC Study), by comparing socio-demographic and nutritional changes that were witnessed between 1965 and 1990 in Japan, and also to describe the study design, the follow-up conditions as of the end of 1997, and the frameworks for analyzing the data of the lung, stomach, pancreas and gallbladder/bile duct, based on the approximately 8-year follow-up data. For other major sites such as cancers of the large intestine and liver, an analysis will be started in the fiscal year of 2002. This paper secondarily aimed to be cited as the basic information on the JACC Study when several publications are to be based on.