In 26 consecutive cases with acquired immunodeficiency syndrome (AIDS) the main cardiac findings were Kaposi's sarcoma in 2 cases, microfocal myocardial abscess in 1, subendocardial infarct necrosis in 2, contraction band necrosis in 13, lymphocytic myocarditis in 9, intramyocardial lymphocytic infiltrates without myocell necrosis in 7 and epicardial lymphocytic infiltrates in 4. No patient had congestive heart failure. However, two-dimensional echocardiography performed in eight patients demonstrated functional abnormalities in six (fractional shortening ranging from 18 to 30%, globular shape, hypokinesia, mild ventricular dilation). Four of these six patients had lymphocytic myocarditis and two had lymphocytic infiltrates in the myocardium and epicardium without myocell necrosis. No lymphocytic infiltrates were seen in the two cases with a normal echocardiogram. Quantitative analysis indicated that involvement of the heart by lymphocytic myocarditis is inadequate in itself to explain dysfunction. It remains to be established 1) whether lymphocytic myocarditis is a possible indication of a more widespread molecular disorder, and 2) what its eventual relation with dilated cardiomyopathy will be.