We report the case of a 13-year-old boy with tetralogy of Fallot and a right-sided aortic arch, in whom a patent ductus joined the pulmonary artery to the left vertebral and subclavian arteries. This caused retrograde flow down the left vertebral artery, and, among other symptoms, dizziness, slurred speech, confusion, and repetitious actions. At surgery, repair was accomplished by infundibular resection, patch closure of the septal defect, and ligation of the patent ductus. Postoperatively, the patient did well without further neurological symptoms and a blood pressure became obtainable in the left arm.