Total plasma cholesterol and lipoprotein fractions were studied before and after 4 months fenofibrate (Lipanthyl®) treatment of 34 hypercholesterolemic adults (16 IIa and 18 IIb), using a concanavalin A precipitation technique. The total plasma cholesterol levels decreased significantly for both IIa and IIb (24 and 18%, respectively, p < 0.001). Fenofibrate reduced the apoprotein B bound cholesterol in IIa and IIb (29 and 27%, respectively, p < 0.001). Apoprotein A bound cholesterol increased significantly in lib (29%, p < 0.001), but there was no significant increase in Ila (11 %). Triglycerides were significantly reduced in both groups. In the light of concanavalin A specificity for apoprotein B and the utility of this technique, it is suggested that the concanavalin A precipitation technique may be applied to hyperlipidemic subjects undergoing treatment with lipid-lowering agents.