When an elderly patient has an abnormal electrocardiogram but no other objective evidence of heart disease, the physician may question whether the ECG is really a reliable index of heart disease in old people or whether aging has some influence on which findings are normal and which are abnormal. The study reported here plus data gathered from an extensive review of the literature indicate the ECG criteria do not have to be changed for geriatric patients. Regardless of age, the prognosis of a specific abnormality remains that of the underlying disease. With age, both heart disease and abnormal electrocardiograms increase in incidence--in a parallel fashion. Specific abnormalities that increase in frequency are first-degree atrioventricular block, bundle-branch block, ST-T wave changes, premature systoles, left anterior hemiblock, left ventricular hypertrophy, and atrial fibrillation. Those that correlate strongly with heart disease are atrial fibrillation, left bundle-branch block, and nonspecific intraventicular condution defect.