A case-control study was designed to elucidate roles of dietary and other behavioral influences, in combination with genetic susceptibility factors (genetic polymorphisms), in colorectal carcinogenesis. Both cases and controls were residents in Fukuoka City and three adjacent areas. Cases were patients undergoing surgery for a first diagnosis of colorectal cancer at 8 hospitals in the study area, and controls were randomly selected in the community by frequency-matching with respect to the expected distribution by sex, age (10-year class), and residence . Dietary and other lifestyle factors were ascertained by in-person interview, and venous blood was obtained for genotyping and possible biochemical measurements. The cases were interviewed at each hospital during the period from 2000 to 2003, and controls were surveyed during the period from 2001 to 2002. A total of 840 cases of colorectal cancer and 833 controls were interviewed with participation rates of 80% for the cases and 60% for the controls. Informed consent to genotyping was obtained from 685 cases and 778 controls. Further details of the design and conduct are described with respect to methodological aspects.