Hereditary syndromes account for a small but important fraction of all cases of colorectal cancer (CRC). Approximately 30% of people with CRC have a family history of the disease, and 5% to 6% have mutations that are diagnostic of a known hereditary cancer syndrome.1 Even though most CRCs are sporadic and most familial CRCs do not arise in the context of a recognized genetic syndrome, it is critical to identify families with hereditary CRC syndromes for 2 reasons: (1) those with a hereditary syndrome and a personal history of CRC have an elevated risk of other noncolorectal cancers as well as a higher risk of metachronous CRC than people without a hereditary syndrome and (2) relatives without a personal history of CRC or other cancers have an elevated risk of CRC and other cancers starting at relatively young ages.