Plant sterols have an extended history of use as cholesterol-lowering agents. Until the 1970s, the principal interest in plant sterols lay in effects of sitosterol, but over the past decade interest has reemerged in using plant sterols in functional foods. Hydrogenated plant sterols have been shown efficacious in lowering lipid levels, inhibiting cholesterol absorption and regressing plaque in animals. Hydrogenated versus unhydrogenated plant sterol esters have been demonstrated to possess equal efficacy in low-density lipoprotein cholesterol lowering in humans. Unhydrogenated plants sterol esters show consistency in cholesterol-lowering across dosage levels in humans. Unhydrogenated, unesterifed plant sterols yield similar low-density lipoprotein cholesterol lowering efficacy as achieved with hydrogenated sitostanol esters. Solubility and miscibility are likely more important determinants in cholesterol-lowering potential of plant sterols than their specific composition.