27 consecutive cases with acute peripheral facial palsy were studied for Lyme borreliosis. In 16 out of 27 children Lyme borreliosis could be diagnosed by detection of specific IgM antibodies in CSF. CSF findings allow a clear distinction according to etiology. All children with facial palsy due to Lyme borreliosis revealed lymphocytic CSF pleocytosis, whereas in cases of unknown etiology CSF was usually normal. Bilateral facial palsy occurred only in children with Lyme borreliosis. All cases with a positive history of tick bite and/or erythema migrans in the head-neck region showed ipsilateral neurological affection suggesting a direct invasion via the affected nerve by Borrelia burgdorferi.