['Hyperproliferation of the colorectal mucosa is regarded as an early step in colorectal carcinogenesis. Deoxycholic acid, a secondary bile acid, stimulates colorectal epithelial proliferation in animals and is considered a tumor promoter in human colorectal carcinogenesis. The aim of this study was to investigate the correlation between colorectal mucosal proliferation and the serum deoxycholic acid level.', 'From each of 19 patients (10 men and 9 women) with (n = 3) or without (n = 16) colorectal adenoma, 18 biopsy specimens were obtained by colonoscopy, 3 from each of the 6 colonic segments. A crude nuclei fraction was prepared, and DNA was stained by propidium iodide to determine the proliferative index (the percentage of cells in the S and G2/M phases of the cell cycle) by flow cytometry. Serum levels of deoxycholic acid were determined by gas-liquid chromatography.', 'The colonic proliferation rates (median of the values obtained in all segments, 14.1%; range, 10.0-18.7%) and the fasting serum deoxycholic acid levels (median, 0.86 micromol/L; range, 0.28-1.58 micromol/L) showed a significant correlation (r = 0.51, P = 0.03). Serum lithocholic, cholic, chenodeoxycholic, and ursodeoxycholic acid levels were not correlated with the proliferation rates.'] Is colonic mucosal proliferation related to serum deoxycholic acid levels?