Special problems face the anesthesiologist in anesthetizing patients with coarctation of aorta. Two patients each 7 years old, a boy and a girl were admitted for surgical correction of coarctation of the thoracic aorta. These patients were premedicated with secobarbital and atropine. One to 1 (1/2) hours later, anesthesia was induced with sodium thiopental and succinylcholine followed by intubation. Anesthesia was maintained with nitrous oxide, oxygen and halothane. A radial artery was cannulated for blood gas sampling and direct arterial pressure, E.K.G., C.V.P. and rectal temperature were monitored continuously. Mild hypothermia (about 34℃) was induced by surface cooling technique with mattress. In each case, in order to repair of coarctation by dacron graft and prosthesis, left atriofemoral by pass was used. Acute hemodynamic changes, such as sudden hypertension of the upper extremity and head following cross clamping of the aorta or profound hypotension following declamping, did not develop with this technique. Possible causes and prevention of hemodynamic changes are discussed.