In a cohort of 710 patients with acute coronary syndromes (ACSs), we demonstrated that the Thrombolysis In Myocardial Infarction Risk Index--a predictor of 30-day mortality in clinical trial patients with ST-elevation myocardial infarction (STEMI)--is a strong predictor of short- and long-term mortality with good discrimination ability (c statistics 0.77 to 0.79) among all subtypes of ACSs (STEMI, non-STEMI, and unstable angina pectoris). These results verify the utility of the Risk Index in unselected patients with STEMI, broaden its application to other types of ACSs, and extend its utility to stratification of long-term mortality risk.