The limited information on co-infection with Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus was a stimulus for presentation of two patients with well-defined double infection of the central nervous system. TBE virus and B. burgdorferi sensu lato infections are searched for in all patients with lymphocytic meningitis and/or meningoencephalitis admitted to our department. During the last ten years we identified two patients who had ELISA IgM and IgG antibodies to TBE virus in serum and a positive PCR result for TBE virus in cerebrospinal fluid as well as B. burgdorferi sensu lato isolated from cerebrospinal fluid. Intrathecal production of borrelial antibodies was not proven in either of the two patients. These findings show that in patients with acute lymphocytic meningitis originating in regions endemic for Lyme borreliosis and TBE, the possibility of concomitant infection should be considered.