Monoclonal antibodies to the SmithKline Beecham Animal Health BRSVR vaccine strain (375 isolate of Bovine Respiratory Syncytial Virus) were produced and then characterized by radioimmunoprecipitation followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, virus neutralization, inhibition of viral-induced fusion and isotype. Nineteen hybridomas produced antibodies that were reactive with the F0, F1, N or P viral proteins of bovine respiratory syncytial virus. One hybridoma (1E72C4) produced antibodies that immunoprecipitated the F0 glycoprotein, neutralized virus (1:8) in the presence of complement, but did not inhibit fusion. Another hybridoma (8B21E7) produced antibodies that immunoprecipitated the F0, F1 and F2 glycoproteins, neutralized virus (1:4) with and without complement and inhibited fusion. Antibodies from 11 hybridomas immunoprecipitated N and F1 proteins, one hybridoma immunoprecipitated the N and P protein, and 5 hybridomas immunoprecipitated the N protein. All monoclonal antibodies were of the IgG2b subtype with either kappa or lambda light chains.