Twelve per cent of a series of 284 patients with vestibular schwannoma presented with sudden deafness. If sudden sensorineural hearing loss is present then it is very likely to be the main presenting symptom. The mean length of patients' history is eight months shorter in this group than in the non-sudden deafness group. Sixteen per cent of vestibular schwannoma patients without sudden deafness present with a 'dead' ear whereas 29.5 per cent of those presenting with sudden deafness have total hearing loss. There was no significant difference between the sudden deafness group and the 'all others' group with regard to tumour size, udiogram shape, caloric test, imbalance, and facial numbness. Although the numbers of patients with sudden deafness in this series were too small to reach significance, on the basis of the clinical correlation of vestibular schwannoma morphology it is possible to postulate that compression of the vasculature within the bony internal auditory canal by a laterally arising tumour may be the aetiological factor and may be more likely to occur than in more medially arising tumours.