Abstract A procedure is described for the identification and quantitation of dietary and fecal neutral sterols by the combination of thin-layer chromatography, mass spectrometry and Liebermann-Burchard colorimetry. The neutral sterols in the diet and feces were extracted by the method of Ho and Taylor and Abell el al. respectively. The extracted neutral sterols were then further separated from other compounds by thin-layer chromatography with silica gel H as adsorbent and a solvent system composed of light petroleum:ethyl ether:glacial acetic acid ( 80:20:1, by volume). The isolated neutral sterols consist of stigmastanol, sitosterol, stigmasterol, campesterol, coprostanol and cholesterol. The relative quantitaty of each sterol in such a mixture can be measured from its mass spectrum. Their relative absorbance of the Liebermann-Burchard reaction can also be determined. Thus, the absolute quantity of each individual neutral sterol in a mixture can be computed from the data obtained from the mass spectrum and colorimetry of the sample. The method is accurate and reproducible and of great value in the study of cholesterol metabolism when the diet and feces contain a variety of plant sterols.