92 patients treated for tick-borne encephalitis (TBE) in the Department for Infectious Diseases, University Hospital Osijek, over a 22-year period (1973-1995) were analysed. The patients were mostly forestry workers. The appearance of the disease followed the biological activity of the tick, with the largest number of affected individuals recorded between April and August. TBE in eastern Croatia is a relatively frequent infectious disease, appearing almost every year. In a smaller number (9.8%) of cases the clinical picture was aseptic meningitis, while in the majority of patients (90.2%) it presented as an acute meningoencephalomyelitic form. The course was relatively severe in the majority of the patients analysed, with disturbances of consciousness (32.6%) and transitory neurological signs (61.9%). Three patients died (3.3%) in the early phase of the disease. A monophasic course dominated. The clinical and epidemiological data were compared with the cases described in other parts of Croatia and regional differences were seen in the severity of illness. These variations could be due to the previously hypothesized different virus subtypes, or to some other unknown factors.