Background: There are very limited data investigating the influence of post percutaneous coronary intervention (PCI) activated clotting time (ACT) level on the in-hospital and short-term clinical outcomes in patients (pts) undergoing PCI with drug-eluting stents (DESs). Methods: A total 1609 consecutive pts underwent PCI with DESs between January 2004 and April 2010 was enrolled for this study. Antithrombotic regimen was combination of subcutaneous enoxaparin (1mg/kg, 2 times a day for 2-3 days) and reduced dose of unfractionated heparin (UFH, 50U/kg) only during the procedure. We checked post PCI ACT levels. The clinical outcomes were compared between the low ACT level group (ACT < 200, n=433) and optimal ACT level group (200 ��� ACT <300, n=1176). Results: Baseline characteristics were similar between the two groups except the optimal ACT group had higher left ventricular ejection fraction (LVEF, 52.1 % vs. 50.7%, p=0.028), more hypertension (66.0% vs. 59.7%, P=0.019), chronic renal insufficiency (3.6% vs. 3.1%, p<0.001), and less likely to present with myocardial infarction (MI, 30.9% vs. 45.4%, p<0.001) and cardiogenic shock (1.9% vs. 3.8%, p=0.031). Although pts with the ACT < 200 level had lower ACT level, but showed similar 1n-hopital and short-term bleeding and vascular complications, clinical outcomes including mortality, Q-MI, repeat PCI, target lesion revascularization-major adverse cardiac events (TLR-MACE) and all MACEs in the univariate analysis (Table). Conclusion: In our study, pts who underwent PCI with DESs had similar in-hopital and short-term clinical outcomes including bleeding and vascular complications regardless of post PCI ACT levels. These finding might be originated from the improved antithrombotic efficacy by hybrid regimen using enoxaparin and reduced dose of UFH, improved stent performance and strong dual or triple antiplatelet regimen.