Starch electrophoresis was employed for the study of the lipoprotein patterns in inborn errors of lipid metabolism. Idiopathic hyperlipemia was characterized by marked increases of cholesterol and phospholipid in the alpha-2-lipoprotein fraction of the serum whereas idiopathic hypercholesteremia showed an increase of these lipids in the beta-lipoprotein fraction. The cholesterol and phospholipid contents in the alpha-1-lipoprotein fractions were diminished in both metabolic errors.