Background: Tachyarrhythmias such as serious atrial and ventricular arrhythmias could occur during percutaneous coronary interventions (PCI) in patients (pts) with ST elevation myocardial infarction (STEMI). However, there were limited data regarding the incidence of tachyarrhythmias and its impact on the long term clinical outcomes in STEMI pts undergoing PCI with drug-eluting stents (DESs). Methods: This study consisted of 2224 consecutive pts underwent PCI from November 2005 to June 2008. Among them, 434 consecutive STEMI pts underwent PCI with DESs were enrolled for the analysis. The angiographic and major clinical outcomes of pts with tachyarrhythmia (n= 32pts, 7.4%) were compared with those of Control group (n= 402 pts, 92.6%) up to 2 years.Results: The STEMI group showed higher incidence of sustained ventricular tachycardia (VT), non-sustained VT, ventricular fibrillation (VF) and atrial fibrillation (AF) compared with those of other two groups. The baseline clinical and procedural characteristics were similar between pts with tachyarrhythmia and those of control group. Six-month angiographic and cumulative clinical outcomes up to 2 years were similar between the two groups except pts with tachyarrhythmia showed higher incidence of cardiac death within 1 month compared with control group but not at 6 to 24 months (Table 1). Tachyarrhythmia itself was not an independent predictor of cardiac death (Adjusted OR: 1.711, 95% CI: 0.443-6.616, p-value=0.436) within 1 month. Conclusions: In our study, the incidence of tachyarrhythmia was higher in STEMI pts and was associated with higher incidence of cardiac death within 1 month. However, development of tachyarrhythmia was not an adverse indicator for worse clinical outcomes in STEMI pts undergoing PCI with DESs.