The therapeutic efficacy of oral acetazolamide has been evaluated in a small pilot study of 14 patients with Menière's disease (23 hydropic ears). Symptomatic improvement was found in 4 cases. In 2 of these patients the improvement was not sustained, whilst another had to stop the drug due to the development of bilateral renal calculi. A deterioration in symptoms was seen in 3 cases. Significant adverse side-effects were encountered in 6 of the 13 patients (46.2 per cent) who complied with drug dosage instructions. It is suggested that this high incidence of side-effects may be consistent with a general metabolic difference between Menière's patients and normal subjects. We conclude that oral acetazolamide has no place in the medical treatment of Menière's disease.