The aim of the study was to determine the usefulness of new immunobiological tests using fractioned human inner ear antigen in the investigation of 4 Menière's disease and 12 rapidly progressive sensorineural hearing loss (RPSNHL). Each patient underwent a full ENT examination and a full range of immunobiological tests comprising ESR, electrophoresis, IgG, A, M, circulating immune complexes, cryoglobulins, complement, organ and non-organ auto-antibodies. The two new tests were the lymphocyte transformation test (LTT) and the immunoperoxidase test against total or fractioned human inner ear antigens. Four main bands were found in electrophoresis with the following molecular weights: 130,000, 45,000, 22,000, and 14,000. The heaviest band corresponded to IgG contained in the inner ear extract. Three cases of bilateral RPSNHL had positive LTT against inner ear antigens. No serum of patients showed a characteristics band with the immunoperoxidase test with regard to the serum of healthy subjects. At least four abnormal inflammatory non-specific tests were shown in the cases of positive LTT. Out of 3, 2 patients received steroids and improved their hearing.