Clear genetic differences in the susceptibility of chickens to visceralinfection by Salmonella have been observed and it has been possible to identifyresistant and susceptible lines of inbred chickens. We report here the resultsof experiments to map directly the gene(s) controlling this trait in chickens byexamining crosses between highly susceptible and highly resistant lines. In themapping panel, a region on chicken Chromosome (Chr) 5 was found to have a largeeffect on resistance, and this effect was observed in three separate resourcepopulations. Mapping of additional marker loci in the region of the resistancegene further localized it to a region of approximately 2 cM, close to the genesfor creatine kinase (CKB) and dynein (DNCH1). This region shows conservedsynteny with telomeric regions of human Chr 14 and mouse Chr 12. On the basis ofthis conserved synteny, this resistance gene seems unlikely to correspond to thepreviously identified salmonellosis resistance genes Lps (located on mouse Chr4) or Nos(2) (located on mouse Chr 11). There was no association between Nramp1and resistance in these crosses, although this gene was shown to contribute toresistance in other crosses. The homologous human and mouse regions at presentcontain no likely candidate genes for this trait. Thus this appears to be anovel resistance gene, which we designate SAL1.