We reviewed the clinical and electronystagmographic findings of 84 patients who presented to our neuro-otology clinic with vertigo of presumed cerebrovascular origin. There was a surprisingly high incidence of isolated episodes of vertigo (abrupt in onset, lasting minutes). In some patients these episodes preceded other symptoms of vertebrobasilar insufficiency or infarction by months. Peripheral vestibular abnormalities were common on electronystagmographic testing; 42% had unilateral hypoexcitability to caloric stimulation. We conclude that the vestibular labyrinth is selectively vulnerable to ischemia within the vertebrobasilar system.