Objectives The purpose of this study was to assess whether transradial access for ST-segment elevation acute coronary syndrome undergoing early invasive treatment is associated with better outcome compared with conventional transfemoral access. Background In patients with acute coronary syndrome, bleeding is a significant predictor of worse outcome. Access site complications represent a significant source of bleeding for those patients undergoing revascularization, especially when femoral access is used. Methods The RIFLE-STEACS (Radial Versus Femoral Randomized Investigation in ST-Elevation Acute Coronary Syndrome) was a multicenter, randomized, parallel-group study. Between January 2009 and July 2011, 1,001 acute ST-segment elevation acute coronary syndrome patients undergoing primary/rescue percutaneous coronary intervention were randomized to the radial (500) or femoral (501) approach at 4 high-volume centers. The primary endpoint was the 30-day rate of net adverse clinical events (NACEs), defined as a composite of cardiac death, stroke, myocardial infarction, target lesion revascularization, and bleeding). Individual components of NACEs and length of hospital stay were secondary endpoints. Results The primary endpoint of 30-day NACEs occurred in 68 patients (13.6%) in the radial arm and 105 patients (21.0%) in the femoral arm (p = 0.003). In particular, compared with femoral, radial access was associated with significantly lower rates of cardiac mortality (5.2% vs. 9.2%, p = 0.020), bleeding (7.8% vs. 12.2%, p = 0.026), and shorter hospital stay (5 days first to third quartile range, 4 to 7 days] vs. 6 [range, 5 to 8 days]; p = 0.03). Conclusions Radial access in patients with ST-segment elevation acute coronary syndrome is associated with significant clinical benefits, in terms of both lower morbidity and cardiac mortality. Thus, it should become the recommended approach in these patients, provided adequate operator and center expertise is present. (Radial Versus Femoral Investigation in ST Elevation Acute Coronary Syndrome [RIFLE-STEACS]; NCT01420614) (J Am Coll Cardiol 2012; 60: 2481-9) (C) 2012 by the American College of Cardiology Foundation