Hereditary Non-polyposis Colorectal Cancer (HNPCC) has only recently been found to be linked to genetic loci. Clinical means of characterizing subjects at increased familial risk remain valid. If conservative criteria for HNPCC are not met, there remains a sufficiently high risk to first-degree relatives of colorectal cancer patients as to warrant enhanced surveillance, ideally by means of colonoscopy. Surveillance study data in support of this area presented in the context of the family histories on which such examinations have been based. Yield of endoscopic testing of at-risk subjects from definite HNPCC families is significant, particularly in the setting of the relatively young subjects studied. No direct comparisons exist between HNPCC subjects, those with minimal family history of colorectal cancer, and healthy family history negative controls. Management of colorectal cancer, whether found at surveillance or on the basis of symptoms, is discussed.