The mortality and morbidity were assessed during a 2-year follow-up in an acute intervention trial in suspected acute myocardial infarction with metoprolol (a selective beta 1-blocker). On admission to the trial, the 1395 participating patients were randomly allocated to metoprolol or placebo for 3 months. Thereafter, if there was no contraindication, patients with infarction and/or angina pectoris were continued on metoprolol for 2 years. A lower mortality was observed after 3 months in patients randomised to metoprolol. The difference remained after 2 years. The difference in 2-year mortality rate was restricted to patients randomised early after onset of pain. Late infarction was observed more often in the placebo group during the first 3 months. When the two groups thereafter were treated similarly, the difference successively declined and did not remain after 2 years. A similar incidence of angina pectoris was observed in the two groups at each check up. During the early recovery period, more patients in the metoprolol group returned to work. No such difference was observed later on.