Background and aim: B-type natriuretic peptide(BNP) has been reported to be a predictor of mortality in Acute coronary syndrome(ACS). However, the relation between BNP level after percutaneous coronary intervention(PCI) and mortality, and the relation between BNP level and major adverse cardiac events(MACE) including death, nonfatal myocardial infarction(MI), target lesion revascularization(TLR), admission with heart failure remain elusive. Methods: In 164 patients(mean age:62짹11yrs, M:F=122:42) with ACS(85patients with ST-elevation MI, 23 with non-ST elevation MI, 56 with unstable angina), serum BNP levels were determined just after hospital admission and for patients treated with PCI, serum BNPs were measured serially at 6 hrs, and 24hrs after PCI. The presence or absence of MACE was determined with phone call contact at 6 months after initial hospitalization orreadmission. Results: 1. 11(6.7%) of 164 patients died and in 22(13%) patients, MACE was observed. 2. Median BNP levels in acute phase were significantly elevated in patients with MACE compared with those without MACE(103 vs 222 pg/ml, p=0.016) 4. BNP level in acute phase was a predictor of MACE independent of left ventricular ejection fraction(LVEF), diabetes mellitus(DM), age by logistic regression model(p=0.044, 95% confidence interval,1.000-1.002). 5. Neither the change of BNP level between pre and post PCI, nor the absolute value of BNP after PCI were related with the occurrence of MACE. Conclusion : Serum BNP level in acute phase, but not after PCI is an independent predictor of short term outcome.