The study included 80 patients treated for sudden deafness over the last 5-7 years. Case history, laboratory findings, pure-tone audiogram and electronystagmography (ENG) findings were noted. If any abnormalities had been recorded in ENG studies, the studies were redone. ORL status was redefined and audiograms were obtained in all patients. When becoming ill, the 80 patients had not differed from the normal population in common cardiovascular risk factors. None of them had had signs of viral infection (paired serum samples had been taken at 2-week intervals routine examinations had been done for common viral antigens). As many as 31 of the 80 patients with acute hearing loss had had abnormalities such as spontaneous nystagmus (PN), hypoexcitability (HE) and directional preponderance (DP) in the bithermal caloric tests (+44 degrees C, + 30 degrees C) of their ENG studies. Twenty of the 31 patients still had abnormal ENG studies after 5-7 years. Only 1 subject had positional nystagmus, and none had subjective vertigo. Patients with an abnormal ENG study showed a poor recovery of the speech reception threshold, whereas those with a normal ENG study showed slightly significant (p less than 0.05) recovery.