The electronystagmographic findings for 116 patients with unilateral idiopathic sudden hearing loss (ISHL) were analyzed. For the purpose of the study, three groups were formed: patients with normal electronystagmographic (ENG) findings; patients with mild to moderate vestibular injuries consisting of spontaneous horizontal nystagmus or directional preponderance; and patients with severe vestibular injuries indicated by reduced vestibular responses, including paresis of the semicircular canal or lack of response to caloric testing. Clinical and audiologic findings were compared. High correlations were found between both subjective vertigo and abnormal ENG findings and the presence of profound hearing loss at the onset of ISHL. There was an inverse relationship between recovery from ISHL and the ENG findings, namely, as the severity of the vestibular injury increased, the percentage of patients who achieved recovery decreased. Patients with abnormal ENGs had a greater mean hearing loss at onset of ISHL and less mean recovery of hearing than did patients who had normal ENG findings. In addition, patients who had abnormal ENG findings recovered less fully from hearing loss in the high frequencies than from those in the low frequencies owing to the proximity of the basilar turn of the cochlea to the vestibular sense organ.