Recent studies confirm the existence of antibodies (Abs) to beta-adrenoceptors in patients with idiopathic dilated cardiomyopathy and Chagas' heart disease. These Abs can be shown to exert both stimulatory and inhibitory effects, which may play a role in the development of the cardiac abnormalities known to occur in these diseases, including advanced heart failure. The hypothesis is advanced that Chagas' heart disease and some forms of idiopathic dilated cardiomyopathy may represent, at least partially, a form of "adrenergic cardiomyopathy."