A new antigenic site was located at the N-terminus of HBeAg. Comparison of antigenic properties of the recombinant proteins HBeAgR and HBeAg delta N truncated at the N-terminus has lead to this conclusion. The proteins have been studied by ELISA and western-blot analysis using monoclonal antibodies E1A7 and polyclonal antiserum to HBeAg. Polyclonal antiserum to HBeAg binds to HBeAg delta N and HBeAgR while monoclonal antibodies E1A7 interact only with HBeAgR. The data obtained supports evidence that the epitope is located at the N-terminus of HBe-polypeptide chain. It is classified as a sequential type one and at least one amino acid from the Met-Asp-Ile sequence participates in its formation.