PURPOSE: The screening test for colorectal polyp is important for the early detection and prevention of colorectal cancer. The aims of this study were to evaluate the characteristic findings and the anatomical distribution of colorectal polyps observed during colonoscopy and to determine proper screening candidates to undergo colonoscopy for colorectal cancer. METHODS: From March 1999 to February 2004, 3,454 asymptomatic individuals underwent total colonoscopy. The number, the location, and the histology of polyps were evaluated retrospectively in 634 patients who had colorectal polyps (453 males and 181 females). The relations among age, location, and histology were analyzed. RESULTS: The mean age was 60 years (range, 15 to 95). Four hundred and twenty-two patients (67%) had a single polyp, and 212 (33%) had two or more polyps. Left-sided polyps were observed in 422 patients (67%), right-sided polyps in 134 patients (21%), and synchronous both-sided polyps in 78 patients (12%). Adenomas were present in 387 patients (61%), and adenocarcinomas were detected in 47 patients (7.4%). There was no definite correlation between location and histology. However the prevalence of right-sided polyps increased with age (P<0.01). CONCLUSIONS: More than 30% of the polyps were located proximal to the splenic flexure. Thus, in the absence of left-sided lesions, an examination of the colon that is limited to the splenic flexure might miss 21% of such lesions. The increasing prevalence of right-sided polyps with age suggests that evaluation of the proximal colon is particularly important in the elderly, especially in those older than 60 years.