The familial incidence of „sporadic“ colorectal carcinoma which does not meet the criteria of hereditary syndromes (familial adenomatous polyposis – FAP and hereditary non-polypous colorectal carcinoma – HNPCC) forms an important risk group which needs a preventive screening strategy. The authors followed-up perspectively for an average period of 15 years (8–18) 205 subjects aged 35–69 years with such a family-histo- ry. The group was divided into two sub-groups according to greater or less significant risk. The subjects were subjected to periodic colonoscopic examinations every three years ( those with a major risk) and every four or five years those with a less significant risk. Only asymptomatic subjects were included without any further risk factors (apart from advancing age). Colorectal carcinoma was detected in 39 probands and adenomas in 77. The classification (DUKES) was distinctly more favourable in this asymptomatic group than in 134 symptomatic patients with a similar family-history and colorectal carcinoma assessed in the stage of clinical symptoms. Their family-history was assessed in the majority only at the time of operation or even later. Five-year survival was in the followed-up asymptomatic group 100 % and in the not followed-up symptomatic group 62 %. Adenomas found in 77 probands and removed by polypectomy were small with a favourable histological structure and mild to medium grade dysplasia. According to age distribution colorectal carcinoma was in the presented study found relatively more frequently in probands under 50 years than in older ones and in probands who had a greater number of relatives with colorectal carcinoma diagnosed before the age of 50 years than in older probands and those who had a more relatives with colorectal carcinoma diagnosed before the age of 50 years than in those with relatives with colorectal carcinoma diagnosed later. As to the further fate of probands the authors recommend in a detailed report to proceed with the hitherto used preventive colonoscopic strategy supplemented by annual tests for occult blood (according to recommendations of the Czech Gastroenterological Society). Conclusion: Subjects with a family-history of colorectal carcinoma (not of the hereditary syndrome type) have a distinctly higher risk of this malignity. This risk does not increase only with the number of affected relatives but also their younger age and the younger age of the subjects themselves. This risk justifies a preventive strategy which leads by periodic colonoscopic examinations recommended from the age of 35 or 40 years to early detection of neoplasia and a more favourable survival period.

        Key words: colorectal carcinoma – sporadic form – familial incidence