Objectives and backround: This study is aimed at determining feasibility and efficacy of using a single guiding catheter for both non-culprit and culprit vessel angiography and intervention during transradial primary percutaneous coronary intervention(PCI) . Methods : This single-center study enrolled 242 consecutive patients with ST-segment elevation myocardial infarction(STEMI) who received primary PCI. Among them, 102 patients received primary PCI via transfemoral approach (TFI), 109 patients received primary PCI via transradial approach using conventional technique (Conventional TRI) and 31 underwent primary TRI using a single guiding catheter (Single Guiding TRI). The used catheter for this purpose was 6 Fr RM짰 3.5 guiding catheter. Results : Using a single guiding catheter, both coronary artery angiograms and intervention were successful in 30/31 patients (96.7%). Needle-to-balloon (N2B) time (from puncture to 1st balloon) and door-to-balloon (D2B) time were similar between TFI and Conventional TRI groups and significant lower in Single Guiding TRI group.(13.8 [TFI] and 14.1 [Conventional TRI] vs. 7.6 minutes, p<0.001; 89.5 [TFI] and 91.0 [Conventional TRI] vs. 68.5 minutes, p = 0.008, respectively), while proportion of patients achieving D2B time within 90 minutes increased significantly in Single Guiding TRI group from 51.0% for TFI and 49.5% for Conventional TRI to 74.2% (p = 0.023). Conclusions: Primary transradial PCI using a single guiding catheter is feasible and highly successful and might allow timely restoration of blood flow in infarct-related artery.