Patients with different heart diseases, dilated cardiomyopathy, valvular heart disease, hypertension, ischemic heart disease or myocarditis showed manifestations of autoimmunity and down-regulation of beta-adrenergic receptors. Autoantibodies against beta-adrenergic receptors in these patients were detected with radioligand binding inhibition assay. The results suggested that the down-regulation of cardiac beta-adrenergic receptors in these patients may be mediated by autoimmunity. Autoantibodies against beta-adrenergic receptor were not related to any specific heart diseases, but to the severity of heart failure irrespective of its etiology. The significance of these autoantibodies in heart failure was discussed.