A rare abnormality associated with right aortic arch in which the sequence of arteries arising from the aortic arch is- right carotid artery, right subclavian artery, then left innominate artery. The latter passes behind the esophagus. This is in contrast to the general rule that the first arch artery gives rise to the carotid artery contralateral to the side of the aortic arch (i.e.- right carotid artery in left aortic arch and left carotid artery in right aortic arch.)