Genetic resistance to avian influenza has previously been associated with a Ser631Asn mutation of the chicken Mx gene. A portion of the Mx gene from 14 genetically diverse chickens lines were PCR amplified and sequenced. The Ser631Asn mutation showed genetic variation among the Iowa State University chicken lines, with some lines having the resistant allele while other lines had the susceptible allele. The diversity in the Mx gene warrants future studies into contrasting host resistance after viral infection in these Iowa State University lines.