Objective: Radial artery harvesting has been questioned because of purported long-term circulatory consequences. Previous midterm Doppler ultrasonographic results are inconsistent regarding ulnar arterial effects. Flow-mediated vasodilatation more sensitively measures response to shear stress as index of arterial reactivity and function. Methods: We contacted 231 patients who had undergone radial artery harvesting at least 10 years previously (mean follow-up, 12.9 ± 0.8 years). Subcohort of 25 volunteers (mean age, 69.2 ± 8.4 years) underwent ultrasonographic evaluation of ipsilateral (harvest) and contralateral (control) ulnar arteries. Flow-mediated vasodilatation compared changes in ulnar arterial diameters before and after occlusion. Results: In subcohort, peak systolic velocity of harvest ulnar artery was 0.82 ± 0.15 m/s, versus 0.63 ± 0.23 m/s on control side (P < .001), with no differences in intimomedial thickness (P = .763) or presence of atherosclerotic plaques (P = .364). Baseline diameter of harvest ulnar artery was 3.0 ± 0.5 mm, versus 2.7 ± 0.6 mm on control side (P = .007). Postocclusion diameter of harvest ulnar artery was 3.2 ± 0.5 mm, versus 2.9 ± 0.6 mm on control side (P = .001). No differences were seen in preocclusion and postocclusion absolute and percentage changes in ulnar arterial diameter (Table 1). Conclusions: Despite increased shear stress, no deterioration in either ulnar arterial structure or functional reactivity was measured by flow-mediated vasodilatation more than 10 years after radial artery harvesting. With appropriate preoperative evaluation, radial arterial grafting for coronary artery bypass grafting is not associated with long-term donor limb vascular insufficiency.