BACKGROUND AND OBJECTIVES: The BNP concentration varies considerably after the onset of AMI, and this makes it difficult to determine the right time to measure the BNP as a valid prognostic marker. The aim of this study was to examine the early changing patterns of BNP and to decide on the suitable time for measuring the BNP as a prognostic marker after the onset of AMI. SUBJECTS AND METHODS: From Feb 2002 to May 2005, we analyzed the changing patterns of BNP in 321 AMI patients. BNP (Triage(R)) was measured at the acute phase (< or = 24 hr), the early phase (2 to 6 day), the late phase (1 to 4 week) & the long-term phase (>4 week) after the onset of AMI. The end points were major adverse cardiac events (MACE) and cardiovascular death (CVD). RESULTS: The mean BNP was 306.2+/-802.8 at the acute phase (mean: 9.5 hours), 251.9+/-592.8 at the early phase (mean: 5.1 days), 103.1+/-172.9 at the late phase (mean: 26.8 days) and 179.7+/-353.3 pg/mL at the long-term phase (mean: 45.9 days). There were no significant differences of the demographic factors between the MACE and Non-MACE group. Multivariative analysis showed that early phase BNP (p=0.007) and male gender (p=0.009) were significant risk factors for MACE. The early phase BNP (p=0.037) and age (p=0.022) were the significant risk factors of CVD. On the ROC curve, the early phase BNP for predicting the CVD risk was 186 pg/mL (AUC=0.87, p<0.001). The Kaplan-Meier survival curve showed that the survival rate was higher for the patients with an early phase BNP<186 pg/mL than it was for those patients with a BNP> or = 186 pg/mL (p=0.000). CONCLUSION: The early levels or changing patterns of the BNP concentrations following AMI showed different patterns of change depending on several prognostic factors. The early phase (2 to 6 day) BNP concentration after the onset of AMI could be used as a significant prognostic marker.