Genetics and genetic testing has become an important aspect in the evaluation of both colon polyps and colon cancer.Every patient with a colon polyp should have a careful family history taken. If necessary, individuals or families can be referred to physicians who specialize in the genetics of diseases who can help with decisions about genetic testing and screening. This is especially important in patients with multiple polyps, several family members with polyps or colon cancer, or a family member with early onset of colon cancer (before age 50).A family history of colon polyps and colon cancer is an important clue to the possible presence of a familial, genetic syndrome. If a syndrome is suspected, individuals can be tested for known mutations, and they can begin surveillance colonoscopies starting at an earlier age; however, there are still syndromes for which mutations are unknown and for which cannot be tested. Nevertheless, even in these latter families, there is a benefit; family members are made aware of the possibility of an unidentifiable syndrome and also may begin surveillance colonoscopies early. Patients with FAP often have other polyps with malignant potential in the gastrointestinal tract and develop polyps and/or cancers in other gastrointestinal and non-gastrointestinal tissues. They require further screening to determine if the non-colonic polyps have malignant potential and if cancer has developed outside of the gastrointestinal tract.Genetics also may be used in other ways. In families with FAP or HNPCC, if the genetic abnormality is identified in the initial family member with polyps or cancer, other family members can be identified with the same abnormality and who then can begin early screening for colon cancer.