Prospectively observed incidences of CRC in path_MLH1, path_MSH2 and path_MSH6 carriers of both genders in the PLSD cohort, in which all patients were subject to colonoscopy surveillance, were up to twice as high as in the retrospective IMRC series that included carriers who did not all receive regular surveillance colonoscopy. The gene discussed is MLH1; the disease is colorectal carcinoma.