Background : Matrix metalloproteinase(MMP) are important for resorption of extracellular matrixes of atherosclerotic fibrous cap inducing coronary plaque rupture. Interleukin-10 (IL-10), known as antiatherogenic factor, downregulates the production of MMP. But clinical implication of the data about IL-10 and MMP in patients with acute coronary syndrome is still obscure. The aim of this study was to assess the early change of these inflammatory biomarkers at initial phase of acute coronary syndrome. Method and Results : Serum levels of IL-6 and MMP-9 as inflammatory biomarker and IL-10, anti-inflammatory biomarker were measured just before primary percutaneous coronary intervention(PCI) in 45 patients with ST elevation myocardial infarction(STEMI) and 15 patients with unstable angina(UA) who were undergone emergency PCI. Blood levels were compared with those of 20 controls with normal coronary angiography. Patients with acute coronary syndrome had significantly higher serum levels of IL-10 and MMP-9 than and controls ( IL-10, p=0.033 and MMP-9, p<0.001). There were no differences in IL-10 and MMP-9 levels between patients with STEMI and UA. No significant correlations were found between IL-10 levels and MMP-9 or IL-10. Conclusion : Serum concentrations of IL-10 and MMP-9 were elevated in initial phase of acute coronary syndrome. This observation may reflect the existence of some other regulatory pathways in acute coronary syndrome.