OBJECTIVE—To describe the mortality during the subsequent 10 years for subsets of patients hospitalised for suspected acute coronary syndrome. PATIENTS AND METHODS—All patients who were admitted to the emergency department in one hospital during 21 months for chest pain or other symptoms raising suspicion of an acute coronary syndrome were registered. From this baseline population three subgroups were defined among those being hospitalised: patients who developed a Q wave acute myocardial infarction (AMI) (n = 306); patients who developed a non-Q wave AMI (n = 527); and patients who developed confirmed or possible myocardial ischaemia (unstable angina pectoris) (n = 1274). These three groups were compared in terms of 10 year mortality. RESULTS—Patients who developed a non-Q wave AMI had the highest 10 year mortality (70.3%), significantly higher than those who developed a Q wave AMI (60.1%; p = 0.004) and those who had confirmed or possible myocardial ischaemia (50.1%; p < 0.0001). There was no difference between patients with confirmed and those with possible myocardial ischaemia (50.0% and 50.1%, respectively). After correction for dissimilarities in age, sex, and history the adjusted risk ratio for death in patients with a non-Q wave AMI compared with Q wave AMI was 1.01 (95% confidence interval (CI) 0.82 to 1.25). The corresponding risk ratio for death in patients with a non-Q wave AMI compared with confirmed or possible myocardial ischaemia was 1.91 (95% CI 1.64 to 2.23). There was also an imbalance in drug regimens among groups. CONCLUSION—This study shows that in a non-selected population of patients hospitalised with a suspected acute coronary syndrome, the highest risk of death is found in those with a non-Q wave AMI and the lowest in those with confirmed or possible myocardial ischaemia. Thus, patients with a Q wave AMI have a long term mortality risk intermediate between the two fractions defined as having unstable coronary artery disease. However, adjusting these results for age and history of cardiovascular disease eliminated the observed difference in mortality between non-Q wave and Q wave AMI. Furthermore, an imbalance in drug regimens might have affected the outcome.