Background Despite successful repair of coarctation of the aorta in childhood, adult survivors often have hypertension at rest or on exercise, and their life expectancy is shorter than normal because of premature coronary and cerebrovascular disease. This may be related to persistent structural and functional arterial abnormalities after surgery.Methods and Results Using high-resolution ultrasound, we studied the right brachial arteries of 25 normotensive young adults who had undergone successful repair of coarctation in childhood (mean age at repair, 62 months; range, 0 to 167 months, including 8 patients operated on in infancy; mean age at study, 19 years; range, 14 to 27 years) and 50 age- and sex-matched control subjects. We assessed the degree of reactive hyperemia (RH) produced after distal cuff occlusion and release and the changes in arterial diameter in response to RH (with increased flow causing endothelium-dependent dilation) and to glyceryltrinitrate (GTN, an endothelium-independent dilator). The response of the right femoral artery to GTN was also measured in 12 coarctation subjects and 12 control subjects. Studies were performed 13.7 years (range, 7 to 21 years) after surgery. RH was significantly lower in coarctation subjects (343+-130% versus 482+-147%), as were endothelium-dependent dilation (3.8+-3.3% versus 8.8+-3.6%) and GTN response (13.3+-6.0% versus 20.5+-6.1%) (P<.001 for each), reflecting abnormal dilatory capacity in both the resistance and conduit arteries. In contrast, GTN-induced dilation in the femoral arteries was similar to that in control subjects (9.5+-2.6% versus 10.1+-4.1%, P=.70). On multivariate analysis, GTN response and systolic blood pressure at peak exercise were inversely correlated (r=-.52, P=.04). Vascular responses were not related to the age at repair.Conclusions Despite successful repair of coarctation in childhood, arterial dilation is significantly impaired in the precoarctation vascular bed of healthy young adults. This may be an important contributor to exercise-related hypertension and late morbidity or mortality. (Circulation. 1994;89: 1745-1750.)