A total of 5778 patients with suspected acute myocardial infarction were randomized to early intravenous metoprolol followed by oral treatment for 15 d, or to placebo. Thereafter, the two groups were treated similarly. During a 1-year follow-up period the mortality in patients who were randomized to early metoprolol was 10.6% compared to 10.7% for placebo (P greater than 0.2). Among patients with a higher risk of death, the tendency towards a reduced mortality in the metoprolol group that was observed after 15 d remained similar after 1 year. It is concluded that early intervention with metoprolol in suspected acute myocardial infarction did not improve the long-term prognosis compared to placebo treatment.