Vestibulocochlear derangements have been studied in three groups of patients: 200 unselected patients with migraine (Series I), 80 migrainous patients referred because of their symptoms for full neurootological examination (Series II), and 116 patients with tension headache who served as controls (Series III), Significant differences were established between tension headache and migraine in respect of incidence and severity of symptoms and their time of onset in relation to the headache. In migraine, vestibulocochlear distrubanees can occur as an aura, accompanying the headache or during headachefree periods, the highest incidence occurring during the headache. In Series I, 59 per cent reported vestibular and/or cochlear symptoms and these were of disabling severity in 5 per cent. Significantly, 50 per cent had a history of motion sickness and 81 per cent experienced phonophobia during the headache, the probable mechanism of which is discussed. Persisting vestibulocochlear derangements were found in 77.5 per cent of Series II, largely vestibular and of both central and peripheral origin. Involvement of the vertebrobasilar vascular system appears to be the most likely explanation. Possible links between Meniere's disease, benign paroxysmal vertigo and migrainc are discussed.