Familial lecithin-cholesterol acyltransferase deficiency is a hereditary disorder of lipid metabolism. Lipid material is deposited in the kidneys, the glomerular capillary basement membrane is irregularly thickened, detachment and even loss of endothelial cells are seen in the glomeruli. Proteinuria was present in 8 out of 9 cases studied, usually it has not been detected before the age of 15–20. After 15–30 years with symptomless proteinuria, terminal renal failure has developed in 6 of the patients. Possible pathogenetic mechanisms of the renal damage is discussed; a large-molecular-weight low-density lipoprotein is suggested to be an important factor.