The pressor response to sympathomimetic agents was studied in dogs with chronic aortic coarctation. In 6-month-old dogs, after coarctation, norepinephrine (NE) produced vasoconstriction in the forelimbs but not in the hindlimbs. In 12-month-old dogs after aortic coarctation, (a) NE and epinephrine caused increase in blood pressure in the forelimbs and decrease in the hindlimbs; latter effect was abolished by β-adrenergic blockade, (b) Tyramine produced a pressor effect in the forelimbs and no change in hindlimb. (c) Isoproterenol caused a fall in blood pressure in both forelimbs and hindlimbs. (d) Angiotensin II increased blood pressure in both forelimbs and hindlimbs; but the response in hindlimbs was lower than in forelimbs