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. It is uncertain that cilostazol is also effective in ST reduction after DES implantation. We investigated the incidence and predictor of stent thrombosis after triple anti-platelet therapy (cilostazol, aspirin and clopidogrel). Methods: The consecutive 839 patients (62.4짹10.4 years, 598 males) after DES stenting were received 100-2000mg aspirin and 75mg clopidogrel for above 9 months plus 200mg cilostazol for one-month. We analysed the baseline charcteristics, angiographic finings, stenting procedure. The angiographically proven acute/subacute ST were defined as ST in this study. Results: Clinical diagnoses were 404 unstable angina (48.2%) and 205 acute ST elevation myocardial infarction (24.4%). A total 1,141 stents underwent successfully 839 patients [370 Cypher and 771 Taxus stents]. Mean stent size and length were 3.21짹0.25mm and 27.0짹5.6mm, respectively. One patient had acute ST(0.17%), five patients had subacute ST(0.59%) and two, late ST(0.23%). Two patients of subacute ST had discontinued antiplatelet therapy prematurely. In 6 patients, 2 patients placed Cypher and 4 Taxus stents. And, one patients died and 5 had non-fetal Q-MI. Total stent length, stent diameter, stent type, age, atherosclerosis risk factor, lesion type were not independent predictor of ST. The multivariate analysis confirmed that bifurcation lesion stenting (odds rato, 41.4, 95%, confidence interval, 8.2 to 208.5), pre-TIMI 0 flow (odds ration, 9.3, 95%, confidence interval, 2.82 to 30.8) were an independent determinant for stent thombosis after DES implantation. Conclusions: This study was showed relatively low incidience of acute/subacute ST in triple antiplatelet therapy after DES stenting. And, predictors of ST were pre-TIMI 0 flow and bifurcation lesion stenting.