One hundred and nineteen serum samples from patients with bilateral sensorineural hearing loss of unknown etiology were investigated for the presence of antibodies against homologous inner ear tissue. 54% of all investigations revealed a binding of serum immunoglobulins even after repeated checks, whereas the investigation of 25 control sera of healthy subjects revealed a false-positive result in only one single case: in this control subject, a manifest rheumatism could be diagnosed later. A correlation between the positive result of the immunofluorescence test and clinical parameters which might indicate a pathoimmune mechanism could not be detected. The question arose as to whether immunologically induced alterations in the region of the human inner ear can be demonstrated at all with the methods of investigation in clinical use today to detect a systemic pathoimmune mechanism.