The chicken lysozyme gene encodes a hydrolase that has a key role in defence, especially in ovo. This gene was resequenced in global chicken populations [red, grey, Ceylon and green jungle fowl (JF)] and related bird species. Networks, summary statistics and tests of neutrality indicate that although there is extensive variation at the gene, little is present at coding sites, with the exception of one non-synonymous site. This segregating site and a further fixed non-synonymous change between red JF and domestic chicken populations are spatially close to the catalytic sites of the enzyme and so might affect its activity.