The effect of radiation on the vestibular apparatus of animals and man have not been widely investigate. Referred symptoms are disequilibrium and spontaneous nystagmus in animals while histological features are intralabyrinthic haemorrhage, edema of the endolymphatic spaces and alterations of sensory hair cells. A group of 20 patients with head and neck cancer located in different sites (nasal cavity, oropharynx, oral cavity, parotid gland) underwent to vestibular investigations before and 3-6 months after radiation therapy. Ten patients (50%) showed an alteration of the vestibular function of peripheral origin after radiation treatment. Complications appeared from a few weeks up to several months following termination of radiotherapy. The slow development of the lesion permitted central compensation. Few patients had symptoms and vestibular symptomatology was always of secondary importance with respect to the initial pathology.