Objective To investigate the cause of high cardiovascular lethality in patients with diabetics mellitus. Methods Sections from autopsied coronary arteries and myocardium of dead patients with non-insulin-dependent diabetics mellitus and 12 dead control subjects were used for histomorphometric studies. Results The coronary atherosclerotic lesion in diabetics patients was not different in severity from those in controls. Nor was there difference in number of myofibers or diameters of myocardic fibers and capillaries.But the capillary density and the ratio of capillary number to myocardic fiber number in diabetics group were significeantly reduced compared with control group(P