The effects of metoprolol treatment in patients surviving acute myocardial infarction have been investigated in a double-blind randomized study. The patients were stratified according to age, infarct size and type of ventricular arrhythmias before administration of metoprolol, 100 mg twice daily (n = 154), or placebo (n = 147). All patients were followed up for 36 months. There were 31 (29 cardiac) and 25 (20 cardiac) deaths in the placebo and metoprolol groups, respectively. Subgroup analyses showed a significant reduction of cardiac death in patients with a large infarct (32.1% with placebo versus 12.5% with metoprolol, p < 0.05) as a result of active treatment.Sudden death rates were 14.7% in the placebo versus 5.8% in the metoprolol group (p < 0.05). The incidence of nonfatal reinfarction was 21.1% in the placebo versus 11.7% in the metoprolol group (p < 0.05). The reduction in nonfatal reinfarction was similar in all pretreatment risk strata. The difference between the two groups in cumulative number of cardiac deaths and patients experiencing nonfatal reinfarction increased throughout the study. Furthermore, cerebrovascular events (p < 0.05) and coronary bypass surgery (p = 0.058) were more frequent in the placebo group.In conclusion, after 36 months of metoprolol treatment after myocardial infarction, there was a significant reduction of nonfatal reinfarction and sudden death in all patients and a reduction of cardiac death in those with a large infarct.