A case-control study has been conducted to investigate the relationship between lifestyle and risk of colorectal cancer. Cases are one hundred patients diagnosed with colon and rectal cancer in Tokai University Hospital between 1986 and 1994. Three controls per case were individually matched by age, sex, local areas and date of health checkups at the Automated Multi-phasic Health Testing and Services (AMHTS) Center of the hospital. The results were analyzed by multi-factorial logistic regression models. Positive history of maternal cancer, large consumption of alcohol, frequent consumption of potato products and white-collar job were predominant risk factors while frequent intake of seaweed was a protective factor. Frequent intakes of dairy foods and lack of exercise showed no significant tendency to increase risk of colorectal cancer. Smoking habits, intakes of meat and egg were shown not to be related to this disease. These findings suggest that family history of cancer and dietary factors play a key role in causation and prevention of colorectal cancer.