Congenital abnormalities of the aortic arch result from aberrant development of one or more components of the embyronic pharangeal arch system. Any component of this system can regress or persist abnormally, resulting in an extensive array of aortic arch anomalies. Clinically, they are classified by those that cause (or are likely to cause) physiolgogical abnormalities and those that do not. Physiologic abnormalities include tracheobronchial compression, esophageeal compression, and abnormal blood flow patteren.