A number of experimental and clinical studies have indicated that the process of aging and diabetes mellitus may result in alterations of cardiac function and composition. These appear to be independent of myocardial ischemia. Left ventricular diastolic compliance is diminished in both situations associated with interstitial collagen accumulation. There is also a reduction in the relaxation rate of the ventricle. In the subclinical state, the aged heart cell undergoes enlargement, but this has not been described in diabetes. In an unknown portion of patients with subclinical abnormalities, the process may advance to abnormalities of systolic function, heart failure, and arrhythmias. There is no convincing evidence that intramural small vessel disease can account for the diffuse cardiomyopathy of these two states. Management requires a particularly cautious use of cardioactive agents.