The present study was devised to determine whether the pattern of hearing loss has any meaning for prognosis in patients with sudden hearing loss. The audiograms and clinical records of 145 patients with sudden deafness between 1991 and 1993 were reviewed. Forty-eight of the patients were females and 97 were males. All patients had been hospitalized and treated with intravenous infusions of naftidrofuryl. The best recovery rate was seen in patients with low-tone hearing losses (68.8% complete and 25% partial recoveries), whereas in patients with high-tone and flat losses the recovery rates were 41.9% and 45.5% respectively for complete recovery and 52.4% and 36.3% for incomplete recovery. The entire group showed an overall recovery rate of 52.4% for complete recovery and 30.3% for incomplete recovery. Immediate treatment resulted in a positive effect on prognosis. Patients under 30 years of age had a somewhat better recovery rate than did older patients. Pre-existing risk factors (diabetes, hypertension, etc.) or accompanying symptoms of vestibular disturbances did not influence prognosis, whereas patients with pre-existing inner ear deafness or with a recurrence of sudden deafness showed relatively lower recovery rates. The possible reasons responsible for exceptionally good prognosis of low-tone hearing losses are discussed.