Outcomes of patients with acute ST-elevation myocardial infarction (STEMI) are directly related to reperfusion time. Effect of transradial approach (left vs right) on reperfusion time has not been fully studied for SETMI patients undergoing primary percutaneous coronary intervention (PCI). The aim of this study was to randomly investigate the efficacy and safety of left radial approach for primary PCI in STEMI patients compared with right radial approach.