The recent emergence of the pandemic H1N1 viruses and their being labeled as ‘swine flu’ has had several detrimental effects on the pork industry. Novel H1N1 strains have been recently detected in swine populations in the United States and in other parts of the world. While the public health significance of these findings is unknown, it is important to determine whether existing vaccines or exposure to previously circulating strains of swine influenza will protect pigs against the novel H1N1. Using a partial two-way cross-hemagglutination inhibition (HI) assay, we have determined a swine H1N1 strain present in a commercial vaccine cross-reacted with antiserum specific to the novel H1N1. We have also shown that a field serum sample with a HI high titer to a ’99 H1N1 strain crossreacted strongly with the novel H1N1. Anti-sera which were specific to the non-pandemic H1N1 strains also crossreacted with the novel H1N1. Therefore, we conclude that current vaccines and circulating non-pandemic H1N1 field strains will provide at least partial protection against the novel H1N1 virus in pigs.