Familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP) are colon cancer predisposition syndromes. FAP is an autosomal dominant inherited condition caused by germline mutations in the adenomatous polyposis coli (APC) gene and characterized by hundreds to thousands of colorectal adenomas. FAP can be classified into several clinical forms, including profuse FAP (> 1,000 adenomas), intermediate FAP (100-1,000 adenomas), attenuated FAP (AFAP) (< 100 adenomas), and gastric polyposis and desmoid FAP (GD-FAP) (< 50 adenomas).FAP patients also have an increased risk of extra-colonic manifestations. MAP is inherited in an autosomal recessive manner. Monoallelic MUTYH mutation carriers are at increased risk for colonic and extra-colonic cancer. Biallelic MUTYH mutations are associated with colorectal polyposis and an increased life-time risk of gastrointestinal cancers.