To ascertain the varieties of neuroborreliosis, 330 patients were identified at the Departments of Neurology in Würzburg and Giessen from 1979 to 1994. Patients who fullfilled at least one of three strict case definitions based on clinical and laboratory criteria were included in the study. Ninety-one per cent of the patients had second-stage neuroborreliosis (duration of symptoms < or = 6 months). The most common syndrome was a painful spinal meningoradiculitis, alone (37%) or in combination with a cranial radiculitis (29%). Meningoradiculitis cranialis (9%), isolated meningitis (4%) and erythema chronica migrans-associated mono/polyneuritis (3%) were further stage II features. Central nervous system involvement occurred either as an acute meningomyelitis or meningomyeloradiculitis (5%) and meningoencephalitis or meningenocephaloradiculitis (4%). Less than 9% of the patients ran a chronic course (stage III) with a disease duration between 6 months and 9 years, either as acrodermatitis chronica atrophicans associated mono- or polyneuritis (2%) or a chronic progressive encephalomyelitis (6%). Cerebrovascular neuroborreliosis (1%) occurred in both stages; however, the primary nature of the course was a chronic one. Involvement of other organs except the skin was rare (joints 3%, heart 1%) but elevated hepatic enzymes were frequent. Our study demonstrates that neuroborreliosis has to be considered in the differential diagnosis of a wide variety of neurological conditions. Cerebrospinal fluid analysis and the search for specific intrathecal antibody production are important diagnostic procedures.