Seven monoclonal anti-idiotypic antibodies (anti-ID MAbs, Ab2) were generated against virus-neutralizing and hemagglutination-inhibiting monoclonal antibody (Ab1) specific for tick-borne encephalitis (TBE) virus. Six of these anti-ID MAbs inhibited the binding of Ab1 to the virus antigen, thus classifying these anti-ID antibodies as Ab2 beta or AB2 gamma. Inhibition tests with heterologous anti-TBE sera revealed that these anti-ID MAbs were not recognized by anti-TBE antibodies and therefore they do not carry an internal image of TBE virus antigen. Hence, the anti-ID MAbs may be classified as Ab2 gamma type. None of the anti-ID MAbs induced production of antiviral antibodies nor protective immunity in syngeneic Balb/c mice. Using these anti-ID MAbs four nonoverlapping idiotopes were identified on Ab1 variable region.