CONCLUSIONS In clinical practice, sudden low-tone loss other than acute low-tone sensorineural hearing loss (ALHL) shows a potential for recurrence. OBJECTIVE ALHL is often associated with recurrence and/or progression to Ménière's disease. We examined the prognosis of patients with sudden low-tone loss who were not classified in the audiometric definition of ALHL. METHODS Sixty-three patients diagnosed at the university hospital with idiopathic sudden low-tone loss of sensorineural hearing loss and without subjective vertigo were followed up in the long term with a mean of over 4 years. The rates of recurrence and/or progression to Ménière's disease for patients with low-tone loss type other than ALHL (non-ALHL) were compared with those for ALHL patients. RESULTS The recovery rate at the initial treatment was 47.6% for non-ALHL and 62.9% for ALHL. A Kaplan-Meier plot indicated that cumulative recurrence rates for non-ALHL were 20.2% at 1 year and 43.5% at 5 years, whereas the rates for ALHL were 12.2% at 1 year and 31.3% at 5 years. There was no statistically significant difference between the two patient groups.