Immunoserological assays of patients with sudden deafness and progressive hearing losses have revealed the presence of different antibodies, leading to the assumption that immunological processes may be involved. Recent investigations have demonstrated that these patients have phospholipid antibodies that can cause venous or arterial vasculopathies. In the present study we analyzed the incidence of these antibodies in patients with inner ear disorders. Sera of 55 patients with sudden deafness and 80 patients with progressive hearing loss were tested. Phospholipid antibodies were demonstrable in 49% of the patients with sudden hearing loss and 50% of the patients with progressive hearing loss. Serotonin and ganglioside antibodies were found in 53% of the patients with sudden hearing loss and 63% of the patients with progressive hearing loss. Since these three antibodies are also frequently found in patients with fibromyalgia syndrome (FMS) and chronic fatigue syndrome (CFS), 28 of the patients studied displayed symptoms typical for these disorders, including fatigue, myalgia, arthralgia, depressions, sicca symptoms and diarrhea. We now recommend questioning patients suffering from inner ear disorders for symptoms typical for FMS or CFS, since these diseases are often closely related to inner ear disorders. If symptoms are present, antibodies should be tested against phospholipids, serotonin and gangliosides. If present, the antibodies are diagnostic for each syndrome. Additionally these immunologic and serologic findings show that these antibodies may play a role in the etiology of hearing loss disorders.