Colorectal cancer affects over 500,000 individuals yearly. Much of the benefit of colorectal cancer screening has been attributed to detection and removal of adenomatous polyps, highlighting the importance of colorectal polyps as targets for intervention and as biomarkers for colorectal cancer risk. Positive familial history (first or second degree relative) for colorectal carcinoma can be found in approximately 30% of all newly diagnosed cases, but less than 5% will be due to a defined genetic category of hereditary CRC. Genome-wide association studies have identified multiple loci at which common variants modestly influence the risk of developing colorectal cancer. The risks conferred by the susceptibility alleles are low. The combined effects may, however, be sufficiently large to be useful for risk prediction, and targeted screening and prevention, particularly as more loci are identified.