Marek's disease (MD) is a lymphoproliferative disease of chickens that costs thepoultry industry approximately $1 billion annually. Genetic resistance to MD isgaining increased attention to augment vaccinal control as disease outbreaksoccur more frequently. Previously, analysis of a 272 F2 White Leghorn resourcepopulation measured for many MD traits and genotyped for 78 microsatellitemarkers revealed two and four quantitative trait loci (QTL) with significant andsuggestive association, respectively, to one or more MD associated traits.Additional genetic markers have since been scored on the MD resource populationto increase QTL resolution and genome coverage. Saturation of four of the QTLregions with 17 markers revealed five new QTL while 32 markers extended thegenome coverage by 400 + CM and uncovered three more QTL. QTL analysis bysingle-point and interval mapping algorithms agreed well when marker saturationwas approximately 20 CM or less. Currently 127 genetic markers coverapproximately 68% of the genome that contain up to 14 MD QTL associated to oneor more MD trait; seven at the significant level and seven at the suggestivelevel. Individually each QTL accounts for 2-10% of the variation and, ingeneral, resistance was dominant although the resistant allele may come fromeither parental line. This study suggests that a limited number of genomicregions play a major role in the genetic control of MD resistance. Markerslinked to these loci may be useful for selection of MD resistant stock by thepoultry industry following verification of the association within their breedingpopulations.