Prognosis in congestive cardiomyopathy (COCM) with marked dilatation and heart failure is poor. A low rate of spontaneous recovery was observed. A high level of circulating catecholamines is often found, which may explain the common finding of resting tachycardia. An early series of COCM patients with tachycardia responded surprisingly well when chronic beta-blockade was added to the conventional treatment of failure. Later, even patients without tachycardia were included with a period of placebo preceding beta-blocker treatment in order to exclude patients with spontaneous recovery. Acute beta-blockade was surprisingly well tolerated, possibly because the reduction in contractility was compensated for by an increase in myocardial compliance. After long-term beta-blockade, improvement was observed after 6 months and further improvement was seen after 24 months. In patients improving functionally, there was reduction in heart size and left ventricular end diastolic diameter and increase in working performance. For the whole group, there was a decrease in rapid filling wave in apex cardiogram, reduction in third heart sound and increase in ejection fraction. Changes in the reverse way were seen in these three variables after beta-blocker withdrawal and relapse into heart failure occurred in 6/15 patients. Changes in diastolic function may be an early important effect of beta-blockade in COCM. Increase in survival was seen when beta-blocker-treated patients with COCM were compared to well matched COCM controls. It is suggested that increased sensitivity to sympathetic stimulation contributes to the pathogenesis in some patients with COCM and that improvement in myocardial function explains prolonged survival.