Electrodiagnostic testing (electromyography, electroneuronography, and blink reflex) and cerebrospinal fluid (CSF) examination (cell count, immunoglobulins, and antigen-specific intrathecal immunoglobulin G synthesis against herpes simplex virus, varicella zoster virus, cytomegalovirus, and Borrelia burgdorferi sensu latu) were performed in 56 patients with Bell's palsy. The CSF was normal in 45 patients and abnormal in 11 patients. Acute borreliosis was the most common specific pathological CSF finding (4 of 11). Electromyography revealed abolished volitional activity in 22% of patients with normal CSF and in 36% with pathological CSF. Electroneuronographic tests with an amplitude decrease of more than 90% on the affected side or abolished responses were found in 20% of patients with normal CSF and in 18% with pathological CSF. Abolished orbicularis oculi reflexes were seen in 67% of patients with normal CSF and in 82% with pathological CSF Concerning electrodiagnostic testing, no statistically significant difference between patients with normal and abnormal CSF was found, so we conclude that electrodiagnostic testing has no indicative value for abnormal CSF in Bell's palsy.