Campesterol and β-sitosterol, two similar plant sterols which differ by only one methyl group in a side chain, were successfully separated using NaY zeolite. The zeolite preferentially adsorbed campesterol over β-sitosterol from a hexane solution. Mathematical analysis of the adsorption kinetics showed that the data could be fitted by a simple irreversible adsorption expression. Molecular modeling showed that the sterol and zeolite pore dimensions are such that size selectivity is the likely mechanism for separation. This hypothesis is consistent with the trend in adsorption rates: as the sterol diameter decreases, the adsorption rate increases in the order cholesterol > campesterol > β-sitosterol > stigmasterol.