Two patients with a right aortic arch and isolation of the left subclavian artery are presented. The clinical findings resulted from relative ischemia of the left arm. There were no features to suggest cerebrovascular insufficiency or congenital heart disease. The esophagograms showed no posterior esophageal compression. In one patient the distal left subclavian artery was opacified by collateral channels from the left external carotid artery through the vertebal artery and branches of the thyrocervical and costocervical trunks. In the other, aortography demonstrated retrograde vertebral flow filling the distal left subclavian artery.