A comparison of data from 58 diabetic and 58 nondiabetic patients with arteriographic evidence of coronary artery disease showed that diabetic patients had a significantly greater frequency of major stenoses in the intermediate coronary artery segments but no significant differences in the proximal or distal segments. Thus, the diabetic patients did have more severe coronary disease, but the diabetic group did not have "more distal" disease as represented by the number of major or minor lesions in the distal segments. The diabetic patients had a significantly greater frequency of electrocardiographic intraventricular conduction defects and manifestations of left ventricular dysfunction. There was no significant difference in the severity of coronary artery disease between the diabetic patients with manifestations of myocardial decompensation and the diabetic patients without such manifestations, suggesting that the increased frequency of myocardial dysfunction in diabetic patients may be related to factors other than the greater severity of coronary artery disease.