Beta-adrenergic blocking drugs have been evaluated for the treatment of arrhythmias and for the prevention of sudden cardia death, particularly in post-myocardial infarction patients. Betablockers have been demonstrated to reduce mortality, reinfarction, ventricular fibrillation and cardiac rupture in acute infarction. Therefore, in patients with suspected myocardial infarction and without contraindications, treatment with betablockers should be initiated early and continued for at least 2 years. Side-effects are mild and occur in approximately 10% of patients. Patients who have contraindications for betablockers use early in myocardial infarction should be reevaluated before discharge from the hospital and considered for such therapy. Because betablockers prevent some of the adverse arrhythmogenic mechanisms seen in chronic heart failure, it may be reasonable to expect that these drugs could have a role in preventing sudden cardiac death in these patients. Analysis of some of the betablocker post-infarction trials indicate that betablockers reduced the risk of sudden death in patients with heart failure at baseline. Some studies demonstrated also the symptomatic improvement following therapy with betablockers in patients with heart failure. But the currently available data are too limited to provide conclusive information.