Background and Purpose: B-type natriuretic peptide(BNP) has been reported by many studies as an effective method of screening LV systolic dysfunction. Conventionally used BNP level of 100 pg/ml may not be the best number in the evaluation of systolic function. We compared the diagnostic value of BNP at different levels(70, 100, 150 pg/ml). Method: 262 patients who were admitted at St. Mary's hospital of the Catholic University had BNP (TriageR) and echocardiogram obtained. LV ejection fraction (LVEF) was calculated using a modified Simpson method, and those with LVEF lower than 50 percent were considered as having LV systolic dysfunction. Sensitivity and specificity of BNP for predicting LV systolic dysfunction were obtained in 56 patients with LVEF< 50% and in 206 patients with LVEF���50% at different level of BNP value.Results: 1) In 262 patients, sensitivity and specificity of BNP for predicting LV systolic dysfunction were 73% and 72% respectively when BNP value of 100 pg/ml or less is normal, 80 % and 65% respectively at BNP below 70 as normal, and 68% and 82% respectively at BNP below 150 as normal. 2) Analyzing only those patients admitted via Emergency room(n=99), sensitivity and specificity for predicting LV systolic dysfunction were 81% and 55% respectively at BNP value below 100 pg/ml as normal, and 76% and 64% at BNP below 150 as normal. 3) 57 patients(22%) had elevated BNP(>100 pg/ml) with preserved LVEF. 22 out of 57 patients had proven coronary artery disease, 11 had tachyarrhythmia, 10 had hypertrophic cardiomyopathy, 11 had valvular heart disease, 2 had conduction disturbance, 3 had renal failure, 4 had left atrial enlargement, 4 had pulmonary hypertension, 1 had pericardial effusion, 1 had pleural effusion. Conclusion: BNP is an effective screening tool in the evaluation of patients suspected having LV systolic dysfunction, especially in patients seeking emergent medical care. In patients with preserved LVEF and increased BNP value, other cardiac conditions should be considered. Setting the cut-off level of BNP higher than conventional level (100 pg/ml) may better eliminate these conditions.