Respiratory disease caused by swine influenza virus (SIV) has become a serious health and economic problem to the U.S. swine industry. Prior to 1998, SIV in the U.S. swine population consisted of a single subtype of the virus, a H1N1 virus comprised of swine genetics. In 1998, a new subtype of the virus emerged, a H3N2 virus that was made up of genetics from avian and human influenza lineage in addition to the swine lineage of the original virus. The emergence of this virus has resulted in viruses that differ genetically. As a result, diagnostics and disease control have become more problematic to the swine industry. The goal of the research reported here was to develop a diagnostic assay that could be used to detect SIV, independent of subtype or genetic makeup. We used proteins in the virus that show little variation to develop this assay. Currently, we have demonstrated that using these proteins, we can detect antibodies in the serum of pigs infected with SIV isolates that differ by subtype and genetic make up. The assay developed will provide information on whether a herd is infected. We hope the assay will assist in determining SIV infection as well as vaccination status.