Colorectal cancer is the third most common malignant neoplasm worldwide. Epidemiological and laboratory animal studies have established a link between various nutritional factors and the etiology of this cancer. Recent studies in genetic epidemiology and molecular biology have shown that inherited genetic factors also play an important role in colorectal carcinogenesis. Thus, genetic-nutritional interactions may form the basis for the development of this cancer. Nutritional factors that appear to promote or attenuate the carcinogenic process in the colon include fat, excess calories, fibre, calcium, selenium, and various vitamins. Strategies for primary prevention of colorectal cancer should therefore be targeted to all populations who are at risk because of dietary and hereditary predisposition. Based on current knowledge, recommended nutrition guidelines for reducing the risk of colon cancer include decreased fat consumption, adequate amounts of fruits, vegetables, and calcium, and avoidance of overweight. Research to further elucidate the role of diet in colorectal carcinogenesis should include randomized studies in humans, testing of various nutritional regimens, and the use of colonic adenomas and markers of cell proliferation and differentiation as end-points.