After successful repair of coarctation of the aorta in childhood, exercise-induced upper body systolic hypertension is well documented. Beta blockade has been shown to reduce the arm/leg gradient in untreated coarctation of the aorta; treatment before coarctation repair has decreased paradoxical hypertension after repair. Ten patients with successful surgical repair of coarctation, defined as a resting arm/leg gradient of less than or equal to 18 mm Hg, were evaluated by treadmill exercise before and after beta blockade with atenolol. Mean age was 5.5 years at repair and 18 at study. At baseline evaluation, systolic blood pressures at termination of exercise ranged from 201 to 270 mm Hg (mean 229 mm Hg). Arm/leg gradients at exercise termination ranged from 30 to 143 mm Hg (mean 84). Follow-up treadmill exercise studies were performed after beta blockade. Upper extremity systolic pressures at exercise termination were normalized in 9 of 10 patients. Maximal systolic blood pressure recorded at exercise termination ranged from 163 to 223 mm Hg (mean 196 mm Hg, p less than or equal to 0.005). Arm/leg gradient at termination of exercise also decreased significantly to a mean of 51 mm Hg (p less than 0.05). No patient had symptoms on atenolol and exercise endurance times were unchanged. The study results in this small series suggest that cardioselective beta blockade can be used to treat exercise-induced upper body hypertension effectively after surgical repair of coarctation. Because a high incidence of premature cardiovascular disease has been well documented after satisfactory surgical repair, the findings are of importance for this group of postoperative patients.