The composition of phospholipids of plasma lipoproteins was studied in normal individuals and in patients with coronary atherosclerosis with type IIb and IV hyperlipoproteidemia using two-dimentional thin-layer chromatography. It was demonstrated that in normals the fractions of lipoproteins of a very low, low and high density have an even distribution of most of the phospholipid components, lecithin and sphyngomyelin being the prevailing phospholipids in all fractions of lipoproteins. In type IIb and IV hyperlipoproteidemia, lipoprotein fractions of very low density have a relatively elevated content of lecithin and those of high density have an elevated content of lecithin and lysolecithin and a decreased level of sphyngomyelin. The obtained data are discussed in terms of the possible effect of the chemical composition of phospholipids on the properties of lipoproteins in atherosclerosis.