A part of low density lipoproteins (LDL) isolated from the blood of healthy subjects and patients with coronary atherosclerosis bind to a Sepharose-linked Ricinus communis agglutinin, a lectin that interacts specifically with galactose residues. Bound LDL can be replaced by galactose, but not other saccharide constituents of the LDL molecule (mannose, glucose, N-acetylglucosamine, sialic acid). Bound LDL subfraction has a 2-3-fold lower content of sialic acid as compared with unbound LDL. The blood content of desialylated LDL in atherosclerotic patients was about 3-fold higher (1.5- to 6-fold) than in healthy subjects. Desialylated LDL induced a 2- to 4-fold more intensive accumulation of total cholesterol in cultured human aortic intimal cells. Unbound LDL had no effect on intracellular deposition of lipids. It is suggested that the subfraction of desialylated LDL may be responsible for the atherogenicity of LDL isolated from blood of atherosclerotic patients.