Objectives and Background; Stent thrombosis is a serious complication of drug-eluting stent (DES) implantation regardless of the timing (acute, subacute, or late). But the actual incidence and predictive factors of stent thrombosis during long term follow up is limited. We investigated the incidence and predictive factors of stent thrombosis after DES implantation during long-term follow-up. Method: A total 1,101 patients with DES implantation were enrolled from March 2003 to December 2005 (1144 sirolimus-eluting stents in 851 patients (1047 lesions; 515 paclitaxel-eluting stents in 258 patients (454 lesions). Stent thrombosis was defined as any of the following after the procedure, as reported in previous studies: angiographic documentation of stent occlusion with or without the presence of thrombus associated with an acute ischemic event, unexplained sudden cardiac death, and MI not clearly attributable to another coronary lesion. Result; Forty patients (3.6%) occurred stent thrombosis during 45.4 months (median duration;15.3 months). Thirty-three patients (3.0%) had late stent thrombosis, 9 of them (0.8%) were documented with angiography and 24 patients (2.2%) died of unexplained sudden cardiac cause. Univariate analysis revealed higher risk stent thrombosis in diabetes, left main PCI, administration of cilostazol, cessation of antiplatelet agents, high creatinine and paclitaxel-eluting stent (p< 0.05). Multivariate analysis showed that the cessation of antiplatelet agents, diabetes, and left main PCI are the independent predictors of stent thrombosis (p< 0.05). Conclusion; The incidence of stent thrombosis was 3.5% and the predictors of stent thrombosis were cessation of antiplatelet agents, diabetes, and left main PCI after DES implantation during long-term follow-up.