Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant condition in which affected individuals develop colorectal cancer or extracolonic cancer, most commonly endometrial, at an early age. Recent advances in molecular genetics have led to the identification of a germline mutation of DNA mismatch-repair genes to be responsible for the majority of HNPPC cases. Since clinical screening of gene carriers can help to prevent cancer, it is important to devise strategies applicable to this syndrome. Recommendations for current management, especially screening and surgical treatment are under study, as they have not yet been clearly established. This paper reviews the clinical presentation, the molecular genetic diagnosis and therapeutic approaches of this syndrome including the controversies concerning prophylactic colectomy for cancer or gene carriers.