All children (less than or equal to 15 years) admitted during 1986 to Sachs Children's Hospital and presenting signs of facial palsy and/or meningitis, or with a history of known tick bite followed by headache, fatigue and muscle pain, were investigated for antibodies to Borrelia in serum and cerebrospinal fluid. (The hospital's catchment area has a high incidence of tick-borne Borrelia infections.) Significantly elevated antibody titre was found in 15 of the 33 patients, in three cases only in cerebrospinal fluid. Eight of the 15 children had facial palsy, which was concomitant with meningitis in six cases. Intravenous penicillin was given to all 15 patients with positive antibody titre, and additionally to three severely ill small children with facial palsy and meningitis. Furthermore, two cases of erythema chronicum migrans, which is considered pathognomonic for Borrelia infection, were treated with penicillin perorally. Cases of Borrelia infection occurred throughout the year, but with a peak in August. To emphasize the variety of symptoms, three cases are presented in some detail.