Recurrent Bell's palsy is a rare form of facial paralysis. To investigate the role which cellular immunity plays in the aetiology of recurrent Bell's palsy, we evaluated a series of such patients using a laboratory test specially formulated to test the cellular immune system. We measured T-lymphocyte and T-lymphocyte subsets in the peripheral blood of 10 recurrent Bell's palsy patients and in 30 healthy volunteers. T-lymphocytes and T-lymphocyte subsets were reduced significantly in the patients, but the T-helper: T-cytotoxic ratio was normal. Cellular immunity abnormalities were therefore found in the peripheral blood of patients with recurrent Bell's palsy, supporting the concept that this is an immunomediated demyelinating disease.