Background and aim: Osteoprotegerin(OPG) is a glycoprotein that acts by competing with receptor activator of nuclear factor-kB(RANK) for binding RANK ligand(RANKL) and plays a critical role in bone remodeling and it has been reported to be associated with the severity coronary artery disease and coronary calcification . The aim of this study is to evaluate the prognostic value of plasma OPG level in patients undergoing percutaneous coronary intervention(PCI) with Drug Eluting Stents(DES). Methods: In 504 patients(mean age: 62짹10, M:F=342/162) underwent PCI with Sirolimus eluting stents(n=388) or Paclitaxel eluting stents(n=157), plasma OPG levels were determined at the time of coronary angiogram. The subjects was consisted of 104 ST elevation myocardial infarcation(MI)(21%), 36 non ST elevation MI(7%), 110 unstable angina(22%), 254 stable angina(50%) patients. Major adverse cardiac event(MACE) was defined as cardiac death, nonfatal myocardial infarction(MI) and target lesion revascularization(TLR) and the presence or absence of MACE was determined with phone call contact at July 2005. Results: 1. Median follow up duration was 11 months ranging from 2 to 27 months. 2. 14 death(2.8%), 1 nonfatal MI(0.2%), 27 TLR(5.3%) was observed during follow up period. 3. Median OPG level was significantly elevated in patients with MACE compared with those without MACE(3322 vs 2821 pg/ml, p=0.012) 4. The unadjusted risk ratio of patients with supramedian OPG level was 2.91(95% confidence interval, 1.46-5.79, p=0.002). 5. In a multivariate Cox regression model, supramedian plasma OPG level remained prognostic factor for MACE after adjusting for age, sex, and Killip Class(p= 0.02, risk ratio, 2.951[95% confidence interval, 1.48-5.89]). Conclusion : Plasma OPG level can be a biochemical prognostic indicator in patients undergoing PCI in the era of drug eluting stent.