The incidence and clinical characteristics of Lyme neuroborreliosis (NB) in a region of high prevalence of tick-bite in Hungary is described. In the county Baranya 66 patients were recorded in a five-year period (1989-93). Fifty-six patients (85%) were in "early", and 10 patients (15%) in "late stage" of NB. The sex distribution was equal. The incidence of NB was 2.9-100,000/year in this region. The incidence of radiculitis/neuritis, meningitis, encephalitis and myelitis in the sample was 56.1%, 19.7%, 18.2% and 6%, respectively. The EEG and evoked potentials showed both central and peripheral neural involvement, EMG and ENG abnormalities were related to the peripheral clinical signs. Non-specific white matter lesions could be found by MRI in 5 patients with central involvement. Cerebrospinal fluid changes were not obligatory but a better indicator of inflammatory process in cases with meningitis and/or encephalitis forms (positivity 75%) than in cases with myelitis and radiculitis (positivity 49%).