Although many studies of coarctation of the aortic isthmus have been reported, none have correlated the hemodynamic, angiographic, and pathologic findings. Of 84 patients (62 male, 22 female; age range, 1 to 49 years, average, 17 years), all had murmurs; 78 had absent, diminished, or delayed femoral pulsations; 51 had cuff systolic blood pressures in the arm above 140 mm Hg, and 30 had diastolic pressures above 90 mm Hg. Fifty-two patients had angiograms. Average pressure gradients (millimeters of mercury) obtained by direct measurements above and below the coarctations in 35 patients were peak systolic, 44; mean, 17; diastolic, 5.