Patients with diabetes mellitus are particularly vulnerable to cardiovascular disease. Although structural and functional myocardial complications are present in patients with diabetes alone, they are particularly severe in patients with both diabetes and hypertension. Considerable evidence-both in experimental animal models and in humans-points to hypertension as of critical importance in the pathogenesis of severe diabetic heart disease. In diabetic hypertensive cardiomyopathy, coronary artery disease as well as structural and functional abnormalities are more pronounced than would be expected from either process alone. The myocardial damage is attributed mainly to hypertension, whereas the myocellular dysfunction is attributed mainly to diabetes. Together, the consequences to the myocardium are devastating. Strict control of the hypertension and diabetes may have an ameliorative effect on the subsequent development of diabetic heart disease.