Monoclonal antibodies (MAbs) against Central European tick-borne encephalitic virus, strain Hypr, were used for determination and characterization of viral antigens of infected PS cells. The MAbs reacted in immunoblotting with flavivirus glycoprotein E (56 kD), and nonstructural protein NS3 (70 kD). According to enzyme immunoassay with infected cells, NS3 antigen is expressed in the plasmalemma.