BACKGROUND - Adoption of transradial percutaneous coronary intervention (TRI) in the United States is low and may be related to challenges learning the technique. We examined the relationships between operator TRI volume and procedural metrics and outcomes. METHODS AND RESULTS - : We used CathPCI Registry data from July 2009 to December 2012 to identify new radial operators, defined by an exclusively femoral percutaneous coronary intervention approach for 6 months after their first percutaneous coronary intervention in the database and ≥15 total TRIs thereafter. Primary outcomes of fluoroscopy time, contrast volume, and procedure success were chosen as markers of technical proficiency. Secondary outcomes included in-hospital mortality, bleeding, and vascular complications. Adjusted outcomes were analyzed by using operator TRI experience as a continuous variable with generalized linear mixed models. Among 54 561 TRI procedures performed at 704 sites, 942 operators performed 1 to 10 procedures, 942 operators performed 11 to 50 procedures, 375 operators performed 51 to 100 procedures, and 148 operators performed 101 to 200 procedures. As radial caseload increased, more TRIs were performed in women, in patients presenting with ST-segment elevation myocardial infarction, and for emergency indications. Decreased fluoroscopy time and contrast use were nonlinearly associated with greater operator TRI experience, with faster reductions observed for newer (<30-50 cases) compared with more experienced (>30-50 cases) operators. Procedure success was high, whereas mortality, bleeding, and vascular complications remained low across TRI volumes. CONCLUSIONS - : As operator TRI volume increases, higher-risk patients are chosen for TRI. Despite this, operator proficiency improves with greater TRI experience, and safety is maintained. The threshold to overcome the learning curve appears to be approximately 30 to 50 cases. © 2014 American Heart Association, Inc.