The present study aimed to investigate the long-term effects of transradial procedures on the radial artery diameter and vasodilator properties. The study included a total of 35 patients (28 males and 7 females) who underwent left transradial coronary angiography with an appropriate indication. The radial artery diameters were measured before and after flow-mediated vasodilation (FMD) and nitrate-mediated vasodilation (NMD). The nonintervened right radial artery served as the control. A marked narrowing in the diameter of the intervened radial artery and impaired FMD response indicating endothelial dysfunction were observed at a mean of 9 months after transradial intervention. Structural and functional changes should be taken into consideration if previously intervened radial artery would be used for interventions, such as arterial bypass graft or dialysis fistula.