Background: The aim of this study was to evaluate the clinical value of serial plasma BNP level assessment after acute exacerbation in congestive heart failure patients. Methods: Between Oct 2002 and June 2003, 88 patients were included. Assessment was by clinical examination, resting 12 lead ECG, chest x-ray, and echocardiography. The blood BNP (Triage짰, Biosite) level, functional status and prognostic parameter were analyzed on admission and at follow-up period (mean 4.5 month). We calculated BNP reduction ratio [100*(baseline BNP- follow-up BNP)/baseline BNP]. We excluded patients with AMI, chronic stable CHF, and CRF. Bad prognositc parameter was defined clinical deterioration or readmission and death. We analyzed the difference between the group with good and bad prognosis. Results: 1. Mean age was 68.7짹9.3 and male was 44.3%(n=39). Most frequent etiology for CHF was dilated cardiomyopathy (n=32, 36.4%). 2. Mean ejection fraction of LV was 41.9짹16.5% and left ventricle end-diastolic diameter was 6.0짹1.0cm. Mean NYHA classification score was 3.03짹0.66 3. Mean baseline BNP level on admission was 899.1짹1062.7 pg/ml and follow-up level of BNP was 463.6짹477.7 pg/ml. Mean BNP reduction ratio was 58.1짹31.4% (-19.2%~95.0%). 4. Clinical deterioration or readmission and death (3 patients) were 11 patients (12.5%). 5. There were no significant differences for baseline BNP level (851.5짹1059.5 vs. 1317.0짹1057.5, p=0.215), follow-up BNP level (390.2짹453.4 vs. 694.3짹 513.4 pg/ml, p=0.145) between the group with good prognosis and bad prognosis. And Age, left ventricular dimension and ejection fraction (42.1짹15.0 vs. 41.2짹23.0%, p=0.891) were no differences between the two groups. Only significant difference between the two groups was BNP reduction ratio (66.4짹25.7 vs. 31.9짹35.2%, p=0.033). In a multivariable model, the BNP reduction ratio was the marker with the strongest relation of bad prognosis (p=0.012). In conclusion, this study demonstrates that the monitoring of BNP level, especially BNP reduction ratio, may predict improving of acute exacerbated status in CHF patients but, further study for the large population will be considered.