Lynch syndrome (LS), or hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomally dominantly inherited disorder that accounts for 1-2 % of colorectal cancer cases. LS is caused by germline genomic alterations in one of the mismatch repair (MMR) genes hMLH1, hMSH2, hMSH6 and hPMS2. The lifetime incidence of colorectal cancer is 20-75 % in these mutation carriers. Individuals with LS-associated colorectal cancer differ from those with sporadic disease in several ways: the tumours are diagnosed at an earlier age; the majority of tumours is located in the proximal colon; there is an increased risk of developing synchronous or metachronous colorectal cancers and the prognosis relatively favourable compared to sporadic cases. It is generally accepted that LS associated colorectal cancers develop along the adenoma-carcinoma sequence as in sporadic cases. There is evidence suggesting that the adenoma-carcinoma sequence is accelerated in LS patients as compared to the general population.