SynopsisSince the histological description of the hamartomatous polyp in 1957 by Horrilleno et al., several different syndromes have been described with the propensity to develop these polyps in the upper and lower GI tracts. These include Juvenile Polyposis, Peutz-Jeghers syndrome, hereditary mixed polyposis syndrome, and the PTEN hamartoma tumor syndromes (Cowden and Bannayan-RileyRuvalcaba syndromes), which are autosomal-dominantly inherited, and Cronkhite-Canada syndrome, which is acquired. The clinical aspects, the molecular pathogenesis, the organ systems affected, the risks of cancer, and the management of these hamartomatous polyposis syndromes will be reviewed in this paper. Although the incidence of these syndromes is low, it is important for clinicians to recognize these disorders in order to prevent morbidity and mortality in these patients, and to perform presymptomatic testing in patients at risk.