The normal left aortic arch courses from the ascending aorta to the left, upwards and backwards in relation to the trachea. The aortic arch branches into the right innominate, left common carotid and the left subclavian artery in sequence. The aortic arch is divided into the proximal transverse arch and the distal transverse arch and the aortic isthmus. Abnormalities of the aortic arch involve obstructive lesions, e.g. coarctation of the aorta, and abnormalities of branching and position of the aortic arch and the latter are topic of this article. Branching and position abnormalities of the aortic arch have clinical meanings: mechanical compression of airway and esophagus by forming a vascular ring or sling, association with cardiac abnormalities, and association with chromosomal abnormalities. This chapter describes anatomical, genetical and echocardiographic features as well as clinical postnatal implications of abnormalities of branching and position of the aortic arch.