Background and Aims: The factors that best predict the presence of colorectal cancers and adenomas at colonoscopy are different. We conducted a prospective multicenter study to evaluate which indications were most closely associated with advanced colorectal neoplasm including colorectal cancer in patients undergoing colonoscopy. Methods: 6752 patients were enrolled in this study between July 2003 and March 2004 from 11 tertiary medical centers in Korea. They were recruited according to itemized 11 colonoscopic indications (1. bowel habit change, 2. stool caliber change, 3. melena/hematochezia, 4. tenesmus, 5. abdominal pain, 6. iron deficiency anemia, 7. past history of colorectal neoplasm, 8. familial history of colorectal cancer, 9. diagnosis and follow-up of inflammatory bowel disease, 10. referred for colonoscopy from primary physician, 11. other indications). The term ‘advanced adenoma’ is used to refer to tubular adenomas that were 10 mm or more in diameter or to tubulovillous, villous or severely dysplastic adenomas irrespective of size. Cancer was defined as the invasion of malignant cells beyond the muscularis mucosa. Advanced colorectal neoplasm was defined as advanced adenoma or invasive cancer. Results: Advance colorectal neoplasm was found in 422/6752 patients (368 advanced adenomas plus 54 carcinomas, 6.25%). In the multivariate analysis, age > 60 (Odds ratio 1.034, 95% confidence interval 1.025-1.043, p < 0.0001), female gender (OR 0.501, 95% CI 0.387-0.647, p < 0.0001), diagnosis and follow-up of inflammatory bowel disease (OR 3.126, 95% CI 1.723-5.674, p < 0.001), referred for colonoscopy from primary physician (OR 1.776, 95% CI 1.135-2.777, p < 0.05), other indications (OR 2.110, 95% CI 1.085-4.103, p < 0.05) were associated with advanced colorectal neoplasm. Conclusions: Age, gender, diagnosis and follow-up of inflammatory bowel disease, referred for colonoscopy from primary physician and other indications are important independent predictors of advanced colorectal neoplasm in patients undergoing colonoscopy. Background and Aims: The factors that best predict the presence of colorectal cancers and adenomas at colonoscopy are different. We conducted a prospective multicenter study to evaluate which indications were most closely associated with advanced colorectal neoplasm including colorectal cancer in patients undergoing colonoscopy. Methods: 6752 patients were enrolled in this study between July 2003 and March 2004 from 11 tertiary medical centers in Korea. They were recruited according to itemized 11 colonoscopic indications (1. bowel habit change, 2. stool caliber change, 3. melena/hematochezia, 4. tenesmus, 5. abdominal pain, 6. iron deficiency anemia, 7. past history of colorectal neoplasm, 8. familial history of colorectal cancer, 9. diagnosis and follow-up of inflammatory bowel disease, 10. referred for colonoscopy from primary physician, 11. other indications). The term ‘advanced adenoma’ is used to refer to tubular adenomas that were 10 mm or more in diameter or to tubulovillous, villous or severely dysplastic adenomas irrespective of size. Cancer was defined as the invasion of malignant cells beyond the muscularis mucosa. Advanced colorectal neoplasm was defined as advanced adenoma or invasive cancer. Results: Advance colorectal neoplasm was found in 422/6752 patients (368 advanced adenomas plus 54 carcinomas, 6.25%). In the multivariate analysis, age > 60 (Odds ratio 1.034, 95% confidence interval 1.025-1.043, p < 0.0001), female gender (OR 0.501, 95% CI 0.387-0.647, p < 0.0001), diagnosis and follow-up of inflammatory bowel disease (OR 3.126, 95% CI 1.723-5.674, p < 0.001), referred for colonoscopy from primary physician (OR 1.776, 95% CI 1.135-2.777, p < 0.05), other indications (OR 2.110, 95% CI 1.085-4.103, p < 0.05) were associated with advanced colorectal neoplasm. Conclusions: Age, gender, diagnosis and follow-up of inflammatory bowel disease, referred for colonoscopy from primary physician and other indications are important independent predictors of advanced colorectal neoplasm in patients undergoing colonoscopy.