Low density lipoproteins (LDL) and four subfractions of very low density lipoprotein (VLDL) were isolated by means of density gradient preparative ultracentrifugation from blood serum of patients with chronic renal failure. Constituents of the fractions were analyzed and physico-chemical characteristics of the lipoprotein particles were studied. These data showed that there are pronounced changes in the composition of VLDL subfractions containing small particles, thus suggesting the impaired catabolism of the particles in blood.