Within 24 months in a consecutive series of 84 children with neurological symptoms indicative of Lyme borreliosis of the central nervous system (CNS) 45 seronegative children (group III), 17 seropositive (group II), and 22 children with specific Borrelia burgdorferi results in cerebrospinal fluid (CSF)-i.e. B. burgdorferi antibodies and/or intrathecally produced B. burgdorferi antibodies and/or positive B. burgdorferi culture in CSF were observed. The results show that intrathecally produced B. burgdorferi antibodies are the most important marker for the diagnosis of neuroborreliosis (with 71.4% positives) and B. burgdorferi cultivation directly from CSF may be successful in the earliest phase of the disease. Since each of the specific CSF parameters may be false negative in some cases, a careful synopsis of laboratory parameters was done. It shows that CSF protein and CSF cell values are higher in group I than in II or III. Neither can seronegativity exclude nor can seropositivity confirm the diagnosis of neuroborreliosis as in only 71% of group I serum B. burgdorferi antibodies were detected. In view of these aspects clinical and laboratory results are discussed.