Diabetics of both types suffer more frequently from atherosclerosis of the coronary, cerebral and peripheral arteries than the non-diabetic population of similar age groups. In the pathogenesis of atherosclerosis in diabetes an important part is played by the very frequent association of the diabetic syndrome with hyperlipoproteinaemia and hypertension, elevated levels of substances potentially toxic for the endothelium such as glucose, chylomicron remnants, sorbitol, immunocomplexes, CO and others. Changes of thrombocyte functions and of the equilibrium of the system prostacycline-thromboxane as well as disorders at different sites of the haemocoagulation an fibrinolytic cascade, no doubt, interfere in a negative way with the process of atherogenesis. Non-enzymatic glycosylation of various proteins probably is also of a certain importance for the process of atherogenesis. The genetic background of the individual has obviously an impact on atherosclerotic complications in diabetics of type 2 (U-allele) where potential atherogenic hyperinsulinaemia is one of the constant manifestations of the disease. The second form of macroangiopathy (mediocalcinosis) affects practically only diabetic subjects and is probably due to the denervation of the blood vessels of the extremities in diabetic neuropathy. Identification and influencing of risk factors of macroangiopathy could have a favourable effect on the quality of life and prognosis of diabetic patients.