An initial full colonoscopy could potentially detect 45 adenomas per 100 of the population, corresponding with a reduction of 60% in the total colorectal cancer risk in the population. Adequate follow-up of the 4% of the population presenting with at least three adenomas could prevent another 6% of colorectal cancers. When the threshold for the initial number of adenomas for deciding on rescreening is reduced to >2 or >1, follow-up would add 12% or 23% respectively to the result of the baseline screening. With initial sigmoidoscopy, immediately followed by a colonoscopy in the case of positive findings, results will be at a relatively high level compared to colonoscopy. Although nearly 50% of cases with adenomatosis may be missed at initial screeni ng, over 70% of adenomas and more than 80% of subjects with multiple adenomas, who will benefit most from endoscopic surveillance, will be detected according to the authors assumptions.