From a large randomized multicentre trial of metoprolol in suspected acute myocardial infarction (n = 5778) we report on the outcome during 1 year of follow-up, in relation to early diagnosis. Patients who developed a confirmed infarction had a 1-year mortality rate of 12.8%. This was significantly higher than the mortality rate of 6.3% (P less than 0.001) in patients with possible infarction and it was also higher than that in patients with no infarction, which was 5.0% (P less than 0.001). A multivariate analysis showed that independent risk predictors in the clinical history of patients without confirmed infarction were a history of angina pectoris, chronic use of digitalis and advanced age. After 1 year, angina pectoris was most common in patients with an initial possible infarction. These patients were also in most urgent need of bypass surgery. We thus conclude that the mortality during 1 year of follow-up among patients with an initially strongly suspected acute myocardial infarction was clearly related to whether or not the patient developed a myocardial infarction.