A case has been described of right-sided aorta with coarctation of the left subclavian artery. The diagnosis was made clinically and by ordinary x-ray film and then confirmed by angiocardiographic films. A small or absent left radial pulse in the presence of a hypertension in the right arm and a normal expected blood pressure in the lower extremities should lead to the consideration of the diagnosis of a localized coarctation of the left subclavian artery. Such causes as cervical rib, anomalous course of the left radial artery, tumors, and aortic aneurysm must first be investigated. With a localized coarctation of the left subclavian artery, just as with the typical coarctation of the aorta, a hypertension is usually present. It is probably a reflex mechanism originating from the nerves in the aortic arch and producing an increased vascular tone in all the extremities. Localized coarctation of the left subclavian artery frequently is discovered by accident. The patient presents no anatomic or physiologic defect in the left upper extremity except the small or absent left radial pulse. Hard work is quite compatible with the lesion.