OBJECTIVES: The incidence and mortality from colorectal cancer among whites have decreased, but they have remained unchanged among African Americans. To explain this disparity, we used the multicenter endoscopy database of the Clinical Outcomes Research Initiative to compare the prevalence of proximal polyps and tumors among asymptomatic African Americans and whites undergoing routine screening colonoscopy. METHODS: African Americans and whites undergoing colonoscopy between January 1, 2002 and September 30, 2003 were considered for analysis. RESULTS: There were 145,175 index colonoscopy reports on unique patients. After applying exclusion criteria, 46,726 patients remained for analysis. Adjusting for age, gender, American Society of Anesthesiologists level, bowel preparation and endoscopic setting, African Americans were less likely to have polyps [adjusted odds ratio (OR) = 0.77; 95% confidence interval (CI) = 0.70-0.84]. However, the odds of having proximal polyps was higher in African Americans (OR = 1.30; 95% CI: 1.11-1.52) compared to whites. In regards to tumors, African Americans were more likely to have tumors (OR = 1.78; 95% CI: 1.14-2.77) and more likely to have proximal tumors than whites (OR = 4.37; 95% CI: 1.16-16.42). CONCLUSIONS: After adjusting for confounders, African Americans undergoing screening colonoscopy in multiple practice settings had higher odds of proximal polyps and tumors than whites, suggesting current colorectal cancer screening recommendations in African Americans should be expanded.