Background: Colonoscopy is the most effective screening tool for colorectal cancer. In Taiwan, colonoscopy is used much less than sigmoidoscopy for screening because sedation significantly increases the cost and is not readily available, and unsedated colonoscopy is considered to be poorly tolerated. However, unsedated colonoscopy has been shown to be well accepted and may improve the cost- effectiveness and access to colonoscopic screening. Objectives; To compare the feasibility of unselected colonoscopy and sigmoidoscopy for primary screening and to analyze factors associated with acceptance of the procedures and need for sedation. Design: Single center, prospective. Setting: National Taiwan University Medical Center. Population and Interventions: A consecutive series of 261 subjects without history of colonoscopy or sigmoidoscopy who underwent unsedated colonoscopy (n = 176) or sigmoidoscopy( n = 85) for primary screening. Main Outcome Measurements: Pain scores, acceptance, and need for sedation. Results: No significant differences in pain, acceptance, and need for sedation were found between the colonoscopy and sigmoidoscopy groups. Only 9.6% in the colonoscopy group and 10.1% in the sigmoidoscopy group considered sedation necessary. Multivariate analyses revealed that the examinee 's sex and the endoscopist, but not the type of endoscopic examination, were associated with the severity of pain and need for sedation. Limitations: Nonrandomized study design. Conclusions: Unsedated colonoscopy for primary screening is well accepted in nine tenths of examinees who accept this option and is similar to sigmoidoscopy in pain, acceptance, and need for sedation. Primary screening with unsedated colonoscopy is feasible, as with sigmoidoscopy. ; 附設醫院內科部 ; 醫學院附設醫院 ; 期刊論文