Blood plasma lipoprotein spectrum and phospholipid spectrum of high density lipoproteins (HDLP) was studied in patients with newly detected noninsulin-dependent diabetes mellitus (NIDDM) and in patients with "secondary failure" of sulfanilamide drugs. Hyperlipidemia, mainly at the expense of increased concentration of triglycerides, very low density lipoproteins, total cholesterol, and low density lipoprotein cholesterol, was detected in the patients. HDLP phospholipid composition was disturbed, with sphyngomyelin level increased and lecithin content decreased. Glurenorm therapy led to reduction of the atherogenicity of blood plasma lipid spectrum despite the persistent basal and postload hyperinsulinemia, thus indirectly indicating an improved function of endogenous insulin. Antiatherogenic effect of glurenorm is evidently mediated by reduction of insulin resistance due to extrapancreatic effect of the drug. Intensive insulin therapy of patients with secondary failure led to a marked reduction of atherogenic components of lipid spectrum. The hypolipidemic effect of insulin therapy seems to be due to recovery of the inhibitory effect of insulin on lipolysis against the background of improved sensitivity to insulin and reduced insulin resistance. A positive effect of insulin therapy on lipid metabolism should not be regarded as an evidence in favor of theoretical assumptions and apprehensions about increased risk of atherogenesis as a result of exogenous hyperinsulinemia.