Background and Purposes Most colorectal tumors develop from adenomatous polyps, which are detected by colonoscopy. African Americans (AAs) have higher incidence of colorectal cancer (CRC) and greater mortality from this disease than Caucasian Americans (CAs). We investigated whether differences in predisposition to CRC and its surrogate (colonic adenomas) between these ethnic groups were related to numbers of cancer stem or stem-like cells (CSCs) in colonocytes. Methods We analyzed colonic effluent from 11 AA and 14 CA patients who underwent scheduled colonoscopy examinations at the John D. Dingell Veterans Affairs Medical Center. We determined proportions of cells that expressed the CSC markers CD44 and CD166 by flow cytometry. Results The proportion of colonocytes that were CD44 + CD166 − in effluent from patients with adenomas was significantly greater than from patients without adenomas ( P  = 0.01); the proportion of CD44 + CD166 + colonocytes was also greater ( P  = 0.07). Effluent from AAs with adenomas had 60 % more CD44 + 166 − colonocytes than from CAs with adenomas. Using cutoff values of 8 % for AAs and 3 % for CAs, the proportion of CD44 + 166 − colonocytes that had positive predictive value for detection of adenomas was 100 % for AAs and CAs, determined by receiver operator characteristic curve analysis. Conclusion The proportion of CD44 + 166 − colonocytes in colonic effluent can be used to identify patients with adenoma. AAs with adenomas have a higher proportion of CD44 + 166 − colonocytes than CA. The increased proportion of CSCs in colonic tissue from AA might be associated with the increased incidence of CRC in this population.