The Japan Multi-institutional Collaborative Cohort Study (J-MICC Study) launched in 2005, supported by a research grant for Scientific Research on Special Priority Areas of Cancer from the Japanese Ministry of Education, Culture, Sports, Science and Technology. Although the main purpose is to confirm and detect gene-environment interactions of lifestyle-related diseases, mainly of cancer, through the cohort analyses, it includes cross-sectional analyses on lifestyle factors, biomarkers, and genotypes, as well as confirmation/screening of new biomarkers usable for early diagnosis of cancer. The endpoints are cancer diagnosis and death. The participants diagnosed as cancer will be identified through population-based cancer registries, hospital cancer registries, mail questionnaires, questionnaires at repeated visits, death certificates, health insurance data, and second survey questionnaires. Subjects are individuals aged 35 to 69 years enrolled from respondents to study announcements in specified areas, inhabitants attending health checkup examinations by local governments, visitors at health checkup centers, and patients at a cancer hospital. The number of subjects was set to be 100,000 throughout Japan. The enrollment period is from April 2005 to March 2010. The second survey is scheduled 5 years after their enrollment. The participants will be followed until 2025. The J-MICC Central Office is placed at Nagoya University Graduate School of Medicine. Ten participating research groups (Cohort Study Executing Groups) send baseline data and blood samples (buffy coat, serum, and plasma) anonymized with an identification number (J-MICC ID) to the Central Office. The data of second survey and follow-up will be linked using J-MICC ID. This study is expected to produce many findings on lifestyle and genetic traits associated with lifestyle-related diseases including cancer among Japanese.