Compression of the trachea and esophagus by vascular anomalies of the aortic arch and its branches may be a threat to life in infancy. The significance of the so-called vascular ring, long recognized as a cause of obstruction of the trachea and esophagus in early life, assumed new importance in 1945 when the operation by Gross1 placed this entity among the surgically correctable congenital lesions of the great vessels. Since that time, experience with the operative treatment of these anomalies has been accumulated.2-4 In the normal 12-mm human embryo, the aortic trunk divides into a left and a right arch. These arches pass on either side of the trachea and esophagus and rejoin to form a single descending dorsal aorta. Normally, a process of absorption or resolution takes place in the right arch distal to the right subclavian, leaving the remaining portion of the right arch to become