The secondary and tertiary structures of the rabies virus spike G protein are important for its ability to induce VN antibodies and confer immunity to the host. For a subunit peptide vaccine to be as effective as the native spike G protein, it would appear that the amino acid sequence comprising the antigenic determinant for VN antibody binding must be made to fold properly even when deprived of its native support structure. Since CNBr peptides have retained at least some of their antigenicity for binding antibodies from hyperimmune serum but not monoclonal VN antibodies, and their immunogenicity, then synthetic peptides containing corresponding sequences should show similar activities. Additionally, determinants that might be necessary for stimulating T lymphocytes would have to be built into the synthetic peptide preparation. It would also appear that a properly folded peptide might have to be aggregated into suitably large particles for it to achieve its full protective effect. Adjuvants may serve in this capacity to enhance the immune response to relevant peptides and thus improve the immunogenicity of a subunit vaccine that ultimately protects animals and humans against rabies virus infection.