Background and Objectives: The use of transradial coronary intervention (TRI) is increasing for its lower rates of major vascular access related complications and the potential for early mobilization. However, the crossover rate from TRI to transfemoral approach was reported between 0% and 12%. Therefore, we evaluated the incidence and predictors of crossover from radial to another vascular access site in patients undergoing percutaneous coronary intervention (PCI) in Korea. Subjects and Methods: Data for PCI of 5,694 patients were collected in TRI working group retrospective registry from 16 institutes in Korea. Total 1,782 patients attempted with transradial approach were evaluated. Results: Crossover of vascular access site from radial to another vascular access site was needed in 64 (3.6%) patients: from radial to brachial artery in 4 patients; to contralateral radial artery in 13 patients; from radial to femoral artery in 47 patients. The most common cause for crossover was need of larger guiding catheter (35.8%). Other causes were radial artery loop or tortuosity (15.1%), radial artery spasm (15.1%), hemodynamic instability during PCI (7.5%), complication at access site (7.5%) and accessing artery stenosis or occlusion (5.7%). Conclusions: In Korea, the rate of access site crossover in patients underwent TRI is low. Need of larger guiding catheter for complex PCI; anatomical factors, spasm and vascular complication of accessing artery; and hemodynamic instability were the predictors of failed TRI.