It is unusual to have a right aortic arch with mirror-image branching of the brachiocephalic vessels and no associated congenital cardiac anomalies. Pathogenetic factors of this anomaly, and associated development of the derivatives of the pharyngeal arches, have not been explored extensively. Eleven patients with a mirror-image right aortic arch and no intracardiac anomalies have undergone evaluation at our institution since 1987. Of these, 4 had stenosis (n = 2) or atresia (n = 2) of the proximal left pulmonary artery. These included 2 with bilateral ductus arteriosus. Six patients had a vascular ring formed by a ductus arteriosus or ligamentum arteriosum from the descending aorta to the left pulmonary artery. Six patients were evaluated for deletion within the DiGeorge critical region of chromosome 22q11. All 6 of the patients with a vascular ring underwent division of the ductus arteriosus or ligamentum through a left lateral thoracotomy. None of the patients with stenosis or atresia of the LPA have undergone intervention. Two of the 6 patients who underwent evaluation for chromosome 22q11 deletion were found to have the deletion. At a median follow-up of 7 years (15 months to 12 years), the patients who underwent division of the ring are all alive and asymptomatic. Two of these patients have undergone repeat magnetic resonance imaging, 1 of whom had mild residual tracheal compression. A right aortic arch with mirror-image branching of the brachiocephalic vessels and no associated intracardiac anomalies is extremely uncommon. We have observed two basic patterns of this lesion: (1) with associated abnormalities of the proximal left pulmonary artery, (2) with a vascular ring formed by a ductus arteriosus or ligamentum from the descending aorta to the left pulmonary artery. Pathogenetic considerations are explored, with a focus on flow-related vascular development and the role of deletions within chromosome 22q11.