Aims The diagnostic and prognostic capacity of biochemical markers of acute myocardial infarction in the emergency department were evaluated in consecutive patients (n=155) with suspected acute myocardial infarction.Methods and Results Serum myoglobin >=110μg.l - 1 and creatine kinase MB m a s s >=5μg.l - 1 had a high accuracy (0.77-0.85) (ns) for acute myocardial infarction diagnosis in patients presenting >2h after symptom onset. Troponin-T (>=0.10μg.l - 1 ) had a lower accuracy (0.53-0.70) for acute myocardial infarction diagnosis, but was the most important 1-year prognostic marker (cardiac death or non-fatal acute myocardial infarction). In patients without ST elevation, combined analysis of two biochemical tests would accurately identify an additional 20% of acute myocardial infarction patients (predictive value of a positive test=0.82) and also identify those without acute myocardial infarction (predictive value of a negative test=0.80). One-year event-free survival was excellent (96%) for patients with two negative biochemical tests, intermediate (74%) for those with discordant tests, and only 53% for patients with two positive biochemical tests.Conclusion Analysis of biochemical tests in the emergency department prior to hospital admission could accurately identify approximately 20% additional acute myocardial infarction patients. The prognosis of these patients is poor, and they may be a target for primary PTCA or new early initiated aggressive medical therapies.