Backgound: Biochemical markers are useful for prediction of cardiac events in patients with acute coronary syndrome (ACS). The N-terminal fragment of the BNP prohormone (NT-proBNP), which is synthesized by cardiac ventricles in response to increased wall stress, may be a prognostic marker in ACS. We assessed the relation between NT-pro BNP levels on admission and major adverse cardiovascular events (MACEs) in a cohort of patients with ACS. Methods and Results: From October 2002 to April 2004, blood samples for NT-proBNP determination were obtained on admission in 78 patients with ST-elevation myocardial infarction (STEMI), 32 with non-ST elevation MI (NSTEMI) and 66 with unstable angina (UA). Patients were followed concerning MACEs (death, MI, heart failure, stroke, revascularization) for 7 months in median. 22 patients (13%) had events. Mean NT-proBNP levels were significantly lower in event-free survivors than in patients with events (1342짹1598 versus 6129짹6522 pg/mL, P <0.0001). The optimal cut-off value of NT-proBNP levels using receiver-operating-characteristic curve was 1445 pg/mL. The unadjusted risk ratio of patients with NT-proBNP levels greater than the threshold was 7.0 (95% confidence interval, 2.6 to 19.0). In a multivariate Cox regression model including clinical background factors and other biochemical markers, the NT-proBNP levels were the most powerful indicator of MACEs (risk ratio, 8.0 [95% confidence interval, 1.7 to 37.1]). Coronary angiographic Gensini score was also a predictor of prognosis in ACS (risk ratio, 3.8 [95% confidence interval, 1.0 to 14.0]). Conclusions: A single measurement of NT-proBNP on admission appears to be useful as a prognostic factor to predict MACEs in patients after ACS. Key Words: Acute coronary syndrome; B-type natriuretic peptides; Prognosis