Vestibular neuronitis is an acute disorder of the vestibular apparatus which manifests by sudden vertigo, without apparent cause, and without auditory or neurological symptoms. Clinically and by thermal stimulation tests, it is characterised by unilateral peripheral vestibular deficit. Evolution is favourable in several days to several weeks and prognosis is favourable, although disorders of moderate intensity may rather often persist, in the form of positional vertigo, sometimes paroxysmal, or disorders of equilibrium on abrupt movement. Careful history-taking and clinical examination, routine evaluation of the vestibular-cochlear apparatus and follow-up of the patient during the first days can eliminate the possibility of vascular cerebellar syndrome, which would require emergency imaging and possibly recuperation by surgery. The aetiology of vestibular neuronitis remains mysterious: inflammatory, viral, vascular? Sedatives acting on the vestibular system should be given for only a very limited time; they inhibit the mechanism of central compensation, which is on the contrary favoured by early vestibular function and rehabilitation.