In order to identify biomarkers of colorectal tumors, 20 subjects with colorectal adenomas were compared with 20 controls as regards fecal parameters (pH, short-chain fatty acids, bile acids, and sterols), blood parameters (bile acids, cholesterol, triglycerides, glycemia and insulinemia), and rectal cell proliferation. Variables were compared by unconditional logistic regression, controlling for gender. There were significant and positive associations between risk of adenoma and total fecal primary bile acids and serum cholesterol, with odds ratios for the third versus first tertile = 9.4 (P for trend = 0.03) and 8.6 (P for trend = 0.04), respectively. There was a trend towards an increased triglycerides level in adenoma subjects compared with controls (P = 0.08). These three parameters correlated with cell proliferation, although cell proliferation itself was not significantly associated with adenomas. In conclusion, these results suggest that fecal primary bile acids and serum cholesterol are markers of early events of colorectal carcinogenesis.