The use of beta-adrenergic blocking agents in patients with congestive heart failure (CHF) is reviewed. The sympathetic nervous system plays an important compensatory role in maintaining inotropic support of the failing heart; therefore, beta blockers have long been considered contraindicated in CHF patients. However, prolonged excessive activation of the sympathetic nervous system may be detrimental. Several clinical trials have shown improved functional status and hemodynamic indices in some patients with dilated cardiomyopathy who received beta blockers. The maximum effect required up to 12 months. Two studies also showed trends toward improved survival. Aspects of study design that appear to be associated with the observation of a favorable response to beta blockade in CHF patients are a low initial dosage, gradual adjustment of the dosage, and a sufficient duration of therapy. Trials with unfavorable results lacked one or more of those design characteristics. Mechanisms proposed to underlie the beneficial effects of beta blockers in CHF patients include up-regulation of beta-receptors, reduction in cardiac energy requirements, protection of the myocardium against norepinephrine toxicity, and anti-arrhythmic effects. Most studies were conducted in patients with idiopathic dilated cardiomyopathy; it is unknown whether beta-blocker therapy is equally beneficial in patients with CHF arising from other causes. Metoprolol is the agent for which there is the most experience; comparative efficacy trials have not been conducted. Beta-adrenergic blockers appear to be beneficial in some patients with CHF. Further trials are needed to identify the patients most likely to respond and the drugs most likely to work.