Cardiac biomarkers have a prognostic value in acute myocardial infarction. Methods. Using aspiration catheter, we collected 80 coronary blood samples at the proximal and distal ends of the culprit lesion during primary PCI in acute STEMI. We measured commonly used cardiac biomarkers [CK, CK-MB, troponin-I(Tn-I), CRP]. VH-IVUS imaging was performed before and after stent implantation during primary PCI. The averaged plaque component was defined as volume divided by # of image slices. Results. Pt age was 57짹13yrs and 94% were males. Greyscale IVUS showed the lesion length was 19.21짹5.60mm, mean vessel area was 17.54짹4.86mm2, mean lumen area was 6.38짹1.77mm2, and mean plaque area was 11.14짹3.62mm2. All of cardiac biomarkers were increased; the following biomarkers were increased at the distal end compared to the proximal end of the lesion: Tn-I(p=0.0446), CK-MB(p=0.0609), and CK(p=0.001)(Table). The measured biomarkers were lower in coronary blood than the peripheral blood, and did not show any correlation with VH-IVUS plaque composition. However, the following correlations between cardiac biomarkers of peripheral blood and VH-IVUS plaque composition were noted: (1) baseline CK did not show any correlation, however peak CK was correlated with averaged % necrotic core(NC)(r=0.473, p=0.0096), and r=0.483 (p=0.008) with the change of CK between peak and baseline value. (2) peak CK-MB was correlated with averaged % NC(r=0.413, p=0.0258), and r=0.471(p=0.01) was in the changes of CK-MB (3) the changes of Tn-I was correlated with averaged % NC(r=0.381, p=0.042), however peak Tn-I was not correlated(r=0.323, p=0.087). The other plaque composition did not showed any correlation with measured cardiac biomarkers. Conclusion. VH measured plaque components may contribute to elevated cardiac biomarkers in pts with STEMI.