Background The Clinical features of the stent thrombosis (ST) following drug eluting stent(DES) implantation is not well known especially in relation to stent fracture (SF) and coronary artery anuerysm(CAA). Method From May 2003 to March 2009. angiographically confirmed ST following DES implantation were retrospectively analyzed. Result 1. The incidence of ST is 1.2 (52/4414)% ( Cypher : 32/2320=1.4%, Taxus 17/1441=1.2%, Endeavor : 1/653 = 0.2%, coroflex 1/22 = 4.5%). 2. The underlying diagnosis for initial PCI were SAP in 19pts(36%), UAP in 22pts(42%) and AMI in 13pts(25%) 3. The diagnosis at the time of ST were AMI 31pts(57%), UAP 12pts(22%),and SAP 11pts(20%) 4. The sites of ST are LAD in 35pts(65%), RCA in 10 pts(18%), CX in 8pts(15%) and LMT in 1pts(2%) 5. Lesion characterstics are CTO in 10pts(18%) and bifurcation in 10pts(18%), 6. The incidence of CAA in previous angiographic the site of ST is 18%(10/54 lesion). 7. The incidence of SF at the time of SF is 14%(8/54 lesion). 8. Reopro was used in 33%(18/52 pts). 9. The TLR rate is 85% (Balloon 66%, BMS 9%, DES 8%, CABG 2%) 10. There were 31 AMI(57%), 5 death(9%), 1 CABG(2%) and 2 CVA(3%) as a complication. 11. At the time of SF, 9 pts took triple antiplatelete agents, 28 pts took dual theraphy, 12 pts took single theraphy and 4 pts took no antiplatelete agent for more than 5 days. Conclusion 1.AMI, bifurcation and CTO are frequent in ST 2.ST is highly associated with MACE 3.ST is closely related to CAA and SF 4.New antiplatelete agent and new dosing strategy of antiplatelete agent may be needed for AMI, CTO, bifurcation, CAA and SF, considering that most SF occurred even with recommended antiplatelete treatment.