Sudden hearing loss is an unexpected presenting complaint in patients with acoustic neurinomas. In our series of patients with eighth cranial nerve tumors, approximately 10% (four of 44 patients) had such a history and their cases are discussed here. All four patients had sensorineural hearing loss and abnormal vestibular responses, but only one showed overt neurological disturbance otherwise. Internal auditory canal roentgenograms and cerebellopontine-cistern myelogram results were abnormal in each case. The factors causing sudden deafness are reviewed, although acoustic neurinomas rarely have been reported. It is suggested that patients with sudden hearing loss be carefully evaluated, including routine internal auditory canal roentgenograms and cerebellopontine-cistern myelography in equivocal cases.