A modification of the indirect enzyme-linked immunosorbent assay (ELISA) was developed which used staphylococcal protein A linked to horseradish peroxidase. Virus [infectious bovine rhinotracheitis, presudorabies, equine herpesvirus type 1, canine adenovirus, feline calicivirus or Herpesvirus hominis] antibodies in equine, bovine, porcine, feline, canine, lagomorphic (rabbit) and human sera were detected using the indirect ELISA in which the antiglobulin enzyme conjugate was replaced by protein A linked to horseradish peroxidase. Results of the ELISA were compared with the results of the serum virus neutralization test. The application of the test in laboratories performing serologic assays with sera from diverse animal species is discussed.