Beta-blockers given within the first 24 hours of an acute MI, first as an intravenous bolus followed by oral therapy, have been shown to reduce in-hospital mortality following a myocardial infarction. For the long-term, beta-blockers represent the only documented effective prophylactic treatment for MI patients. The reduction in all-cause mortality is due primarily to a reduction in atherosclerotic cardiovascular deaths, particularly sudden cardiac deaths. This finding is consistent with the experimental observation that beta-blockers raise the threshold for ventricular fibrillation. Indeed, MI patients with complex ventricular arrhythmias respond very favorably to beta-blockers. However, reductions in nonsudden deaths and nonfatal reinfarctions have also been observed, suggesting that the beneficial effects of beta-blockers are not limited to antiarrhythmic effects alone and that these drugs may also have anti-ischemic effects. The prime candidates for beta-blocker therapy are the high-risk MI patients with transient electrical and/or pump complications during the acute phase. If therapy is initiated within hours of an acute infarction, it seems reasonable to continue it after hospital discharge. Evidence from the large, long-term trials suggest that, in the absence of any troublesome adverse reaction and given that most post-MI patients experience ventricular arrhythmias and angina, it seems reasonable not to limit the duration of treatment.