A highly efficient technique has been developed for the resolution of several sterols that are intermediates in the biosynthesis of cholesterol and that differ only by one carbon-carbon double bond or by one methyl group. The technique described utilizes reverse-phase high-pressue liquid chromatography on a micronBondapak-C18 column with acetonitrile as eluting solvent. This procedure is capable of measuring the enzymatic conversion of desmosterol to cholesterol. This chromatographic separation can be conducted by reverse-phase high-pressure liquid chromatography in approximately 10 min, whereas other procedures can require several days.