Background : The plasma brain natriuretic peptide (BNP) levels on admission have been reported to increase and predict mortality in patients with acute myocardial infarction. We investigated whether the plasma BNP level on admission in patients with acute ST elevation myocardial infarction (STEMI) could predict the status of myocardial tissue perfusion after primary percutaneous coronary intervention (PCI). Method : In 102 patients with STEMI underwent primary PCI. The plasma BNP, CRP, troponin T and CK-MB levels were measured on admission. The status of myocardial tissue perfusion was assessed by ST-segment resolution, corrected TIMI frame count (CTFC), and myocardial blush grade (MBG) immediately after primary PCI. All patients were divided into two groups according to the BNP levels; patients with higher (H group, ��� 80 pg/ml, n= 43 ) and those with lower BNP levels (L group, < 80 pg/ml, n=59 ). Major adverse cardiac events were compared one month later between two groups. Result : There were no differences in demographic and angiographic characteristics between two groups. H group showed significantly higher troponin T (3.025 + 4.26 vs 0.196 + 0.355 ng/ml , P<0.001) and higher CRP level on admission (5.37 + 5.12 vs 4.64 + 1.53 %, P<0.001). In H group, less rapid resolution of ST segment (42.69 + 24.85 vs 71.15 + 19.37 %, P<0.001). H group showed high frequency on major adverse cardiac events of 1 month( 0.35 + 0.68 vs 0.03 + 0.13 %, P <0.001) Conclusion : Acute STEMI patients with higher BNP levels on admission showed inadequate myocardial tissue perfusion status after primary PCI. The plasma BNP level on admission may serve as an predictor of tissue perfusion after reperfusion therapy in patients with STEMI.