Content of lecithin as related to the total content of phospholipids was increased in alpha-lipoproteins of healthy men with hyper-alpha-lipoproteinemia (concentration of cholesterol exceeded 72 mg% in the lipoproteins). The alpha-lipoproteins accumulated considerably more free cholesterol than its esters; this caused a decrease in the molar ration "phospholipids/free cholesterol". The surface of phospholipid-cholesterol monolayer of alpha-lipoproteins is apparently responsible for retaining of increased amounts of cholesterol in the complex as well as for participation of these structures in enzymatic reactions in blood serum.