Familial polyposis is a genetically-transmitted disease characterized by multiple adenomatous colorectal polyps and a high risk for development of adenocarcinoma. Familial polyposis and Gardner's syndrome should be differentiated from other penetically-linked polyposis syndromes lacking a predisposition for cancer. Total colectomy and ileorectal anastomosis, aggressive follow-up and intensive surveillance of non-polyp bearing relatives can reduce the risk of developing cancer. From an epidemiologic point of veiw, polyposis is a valuable model for the study of the interaction of genetic and environmental factors in the genesis of colon cancer.