Background: Drug-eluting stents (DES) have dramatically reduced the rate of restenosis. However, concerns have been raised regarding the stent thrombosis (ST) with the unrestricted use of these stents. Therefore, we investigated the incidence, predictors, and clinical outcome of ST after successful DES implantation. Method: This study comprised all patients who underwent DES implantation at Seoul National University Hospital and Bundang Seoul National University Hospital from March, 2003, through March, 2005. We collected whole data of all patients from medical records and by telephone contact. Possible ST (sudden death, fatal out-of-hospital cardiac arrest, or myocardial infarction (MI), not clearly attributable to another coronary lesion) as well as angiographically proven ST were defined as ST in this study. The following variables were entered into the multivariate model: diabetes, acute coronary syndrome, side branch intervention in bifurcation lesions, chronic total occlusion, thrombus, heavy calcification, Taxus stent, and in-stent restenosis(ISR) lesion. The cases of ST after premature discontinuation of antiplatelets were excluded in the regression analysis. Results: During the study period, a total of 1308 consecutive patients underwent successful implantation of Cypher ( 890 patients, 1157 lesions, 1364 stents) or TAXUS ( 378 patients, 524 lesions, 666 stents) stents and 13 patients(1.1%, possible ST in 6 patients) had 14 cases of ST(Cypher:7(0.8%), TAXUS: 6(1.6%); P=0.28). One patient had acute ST(0.08%), 7, subacute ST(0.6%) and 5, late ST(0.4%). Two patients had discontinued antiplatelet therapy prematurely. Among these 13 patients, 8 died (case fatality rate, 62%):4 fatal MI, 4 sudden cardiac death. Independent predictors of ST were side branch intervention (OR: 4.69; 95% CI, 1.19-18.46; P=0.027), DES implantation for bare metal stent(BMS) ISR(OR: 4.28; 95% CI, 0.87-21.17; P=0.075) and heavy vascular calcification (OR:5.44; 95% CI, 1.36-21.72; P=0.016). Conclusions: About one third the cases of ST occurs in late period after DES implantation. Side branch intervention, DES implantation for BMS ISR and heavy vascular calcification were identified as predictors of ST.