P ercutaneous coronary intervention (PCI) has traditionally been performed using femoral arterial access.1 Risks associated with transfemoral PCI (f-PCI) include access site bleeding and major vascular complications, which are associated with a risk of subsequent morbidity, mortality, and costs.2 Alternative vascular access sites for PCI include the brachial, radial, and ulnar arteries.3 Data from singlecenter and small randomized trials comparing transradial PCI (r-PCI) with the femoral approach suggested a lower rate of bleeding and vascular complications associated with r-PCI. 4 More recently, a large randomized trial of patients with acute coronary syndrome (ACS) undergoing coronary angiography or intervention, demonstrated that both radial and femoral approaches were equally effective and safe, with a lower rate of vascular complications in the radial approach cohort. 5 In addition, the high-risk subgroup of patients with ST-segment elevation myocardial infarction had a reduction in cardiovascular events, driven by an apparent reduction in mortality in the r-PCI group. A subsequent meta-analysis of observational and randomized studies showed that r-PCI was associated with a 78% reduction in bleeding in comparison with f-PCI. 6 Despite this growing body of evidence, data fromBackground-Radial access for percutaneous coronary intervention (r-PCI) is associated with reduced vascular complications; however, previous reports have shown that <2% of percutaneous coronary intervention (PCI) procedures in the United States are performed via the radial approach. Our aims were to evaluate temporal trends in r-PCI and compare procedural outcomes between r-PCI and transfemoral PCI. Methods and Results-We conducted a retrospective cohort study from the CathPCI registry (n=2 820 874 procedures from 1381 sites) between January 2007 and September 2012. Multivariable logistic regression models were used to evaluate the adjusted association between r-PCI and bleeding, vascular complications, and procedural success, using transfemoral PCI as the reference. Outcomes in high-risk subgroups such as age ≥75 years, women, and patients with acute coronary syndrome were also examined. The proportion of r-PCI procedures increased from 1.2% in quarter 1 2007 to 16.1% in quarter 3 2012 and accounted for 6.3% of total procedures from 2007 to 2012 (n=178 643). After multivariable adjustment, r-PCI use in the studied cohort of patients was associated with lower risk of bleeding (adjusted odds ratio, 0.51; 95% confidence interval, 0.49-0.54) and lower risk of vascular complications (adjusted odds ratio, 0.39; 95% confidence interval, 0.31-0.50) in comparison with transfemoral PCI. The reduction in bleeding and vascular complications was consistent across important subgroups of age, sex, and clinical presentation. Conclusions-There has been increasing adoption of r-PCI in the United States. Transradial PCI now accounts for 1 of 6 PCIs performed in contemporary clinical practice. In comparison with traditional femoral access, transradial PCI ...