Repair of coarctation of the aorta may not prevent the subsequent development of elevated systemic blood pressure at rest or with exercise. The correlates of late postoperative resting systolic blood pressure and maximal exercise systolic blood pressure levels were investigated in a retrospective study of 42 patients who had graded exercise tests after correction of coarctation of the aorta. The independent variables studied included height, weight, body surface area, age at surgery, age at exercise testing, the time interval between surgery and exercise testing, the highest systolic blood pressure prior to surgery, gradient across the coarctation at preoperative catheterization, and the residual postoperative gradient across the coarctation. The same combination of independent variables provided the best regression model for explanation of the variance of both postoperative resting and maximal exercise systolic blood pressure. The models included height, highest preoperative systolic blood pressure, and residual gradient. None of the other variables added significant explanatory ability to either model. These findings suggest that the preoperative level of systolic blood pressure may be the best determinant of timing the corrective surgery. It may be possible to defer the operation, as long as blood pressure remains normal, until an age when repair is less likely to result in recurrent coarctation.