A 76-year-old female presented with vertebrobasilar insufficiency due to a severe stenosis of the right primitive hypoglossal artery (an unusual carotid-basilar anastomosis) manifesting as recurrent transient ischemic attacks (TIA) associated with quadriparesis and cerebellar ataxia with vertigo, nausea, and vomiting. She had been treated with 100 mg of aspirin per day, but TIA associated with the same symptoms persisted. Cerebral blood flow (CBF) studies disclosed a region of moderately low flow in the posterior fossa. Cerebral angiography demonstrated that the posterior fossa was supplied via the right primitive hypoglossal artery, which was severely stenotic at its origin. Percutaneous transluminal angioplasty using a Stealth catheter, 3.0-mm diameter and 10-mm long, successfully dilated the stenosis. No TIA occurred postoperatively, and a marked increase in CBF was demonstrated in the posterior fossa.