The adsorption techniques for removing the β-lipoprotein and both the α-lipoprotein and the β-lipoprotein from sera have been examined. New findings include: 1.A preβ-lipoprotein: β-lipoprotein cholesterol ratio greater than 0.4 in the Frederickson types III, IV and V; 2.A good correlation between the cholesterol and the triglyceride in the preβ-lipoprotein and a poor correlation in the β-lipoprotein; 3.The characteristics of a ‘midβ-lipoprotein’ which moves between the β-lipoprotein and the preβ-lipoprotein during electrophoresis in agar. It is not adsorbed by light magnesium carbonate yet is adsorbed by the mixture of light magnesium carbonate and magnesium trisilicate, can be found in normal sera, appears increased in Frederickson's type lib phenotype, apparently still has α-lipoprotein antigenic determinants, and seems to bind very little cholesterol; 4.Estimations for corrections that may be applied to allow for the α-lipoprotein cholesterol that is removed by the adsorption with light magnesium carbonate. Approximately 38-40% of the α-lipoprotein cholesterol is removed, yet the carrier protein appears relatively resistant to adsorption even by the magnesium carbonate and trisilicate. The removal of β-lipoprotein cholesterol causes the β-lipoprotein cholesterol to be read too high unless corrections are applied. The adsorption techniques for removing the β-lipoprotein and both the α-lipoprotein and the β-lipoprotein from sera have been examined. New findings include: 1.A preβ-lipoprotein: β-lipoprotein cholesterol ratio greater than 0.4 in the Frederickson types III, IV and V; 2.A good correlation between the cholesterol and the triglyceride in the preβ-lipoprotein and a poor correlation in the β-lipoprotein; 3.The characteristics of a ‘midβ-lipoprotein’ which moves between the β-lipoprotein and the preβ-lipoprotein during electrophoresis in agar. It is not adsorbed by light magnesium carbonate yet is adsorbed by the mixture of light magnesium carbonate and magnesium trisilicate, can be found in normal sera, appears increased in Frederickson's type lib phenotype, apparently still has α-lipoprotein antigenic determinants, and seems to bind very little cholesterol; 4.Estimations for corrections that may be applied to allow for the α-lipoprotein cholesterol that is removed by the adsorption with light magnesium carbonate. Approximately 38-40% of the α-lipoprotein cholesterol is removed, yet the carrier protein appears relatively resistant to adsorption even by the magnesium carbonate and trisilicate. The removal of β-lipoprotein cholesterol causes the β-lipoprotein cholesterol to be read too high unless corrections are applied.