Consecutive patients admitted to our hospital with suspected acute myocardial infarction during 21 months were prospectively evaluated. One-year mortality after discharge from hospital was related to whether or not an infarction developed (infarct versus non-infarct patients). Of patients discharged alive after developing an infarct, there was a mortality of 17% (n = 777) versus 12% (n = 1830) (P less than 0.001) for all patients not developing infarction. In a high risk group (any of the following: age greater than or equal to 75 years, previous history of myocardial infarction, diabetes mellitus or congestive heart failure) patients developing infarction had a mortality of 24% (n = 457) versus 17% (n = 1221) for those who did not (P less than 0.001). In a low risk group (none of the high risk criteria), the corresponding mortality was 8% (n = 316) for patients suffering infarction and 3% (n = 603) for those not having infarction (P less than 0.001). The difference in mortality between patients with and without infarction was most marked in women (21% vs 11%; P less than 0.01) and in hypertensives (25% vs 12%; P less than 0.001), but less marked in men (16% vs 13%; NS) and in patients without hypertension (13% vs 12%; NS). Among patients not suffering infarction, mortality was particularly high in those with previous congestive heart failure (23%) and diabetes mellitus (21%).