BACKGROUND: A third-generation troponin T assay with improved precision and a lower detection limit has been developed. However, the appropriate cutoff for identifying patients with the acute coronary syndrome who are at low risk of subsequent mortality has not been established. METHODS: A retrospective evaluation of data from the Fragmin and fast Revascularization during InStability in Coronary artery disease II (FRISC-II) trial suggested that a cutoff below 0.1 microg/L for troponin T levels might be more useful in risk stratification. A prospective validation of two cutoff levels (0.03 microg/L and 0.01 microg/L) was performed in 7115 patients with non-ST-elevation acute coronary syndrome from the Global Utilization of Strategies To open Occluded arteries IV (GUSTO-IV) trial. RESULTS: Patients with troponin T levels >0.1 microg/L had greater 30-day mortality (5.5% [201/3679]) than did those with levels