Ultimately, the genetics of all colorectal cancers will be elucidated, perhaps resulting in the development of reliable blood testing to replace screening tests that are expensive, resource intensive, and have some associated risk. At present, the variations of familial adenomatous polyposis (FAP) with mutations of the APC gene as well as the multiple mismatch repair (MMR) genes involved in the basic phenotype of hereditary nonpolyposis colon cancer (HNPCC) represent a minority of all colon cancer patients. Attenuated FAP, a mutation of the APC gene, exhibits a different phenotype than classic FAP characterized by fewer polyps and later age of onset. More recently, the recessive MYH genes, with an attenuated FAP phenotype but a different genetic transmission, have been added to the better-known genetic syndromes.4 As more of the genetic associations are elucidated, the molecular basis of sporadic colorectal cancers will become evident.