One of the major determining factors in the price of market hogs today isbackfat depth. Therefore, identification of regions of the genome affecting thistrait could be very useful to the swine industry. A large resource population (n= 540) was developed by backcrossing F1 Meishan-White composite females toeither Meishan or White composite boars. A genomic scan was conducted bygenotyping all animals with microsatellite markers spaced at approximately 20-cMintervals across the entire porcine genome. Breed of origin for all chromosomalsegments was determined using multipoint linkage procedures, and a least squaresregression analysis was conducted. Nominal P-values were converted to agenome-wide level of significance to adjust for the numerous tests conducted.Traits analyzed were backfat depths at the first rib (FRIB); 10th rib (10th);last rib (LRIB); last lumbar (LLUM) vertebra; the average of FRIB, LRIB, andLLUM (AVBF); and weight of leaf fat (LEAF). Significant quantitative trait loci(QTL) were detected on chromosomes 1, 7, and X. Suggestive evidence for QTL waspresent on chromosomes 5, 8, 9, 10, 13, and 14. Genotypic means for the locidetected indicated a predominantly additive mode of inheritance. Meishan allelesproduced fatter pigs for all loci except those on chromosomes 7 and 10.Additional research should be conducted to refine the estimated position of eachQTL and its effect and determine epistatic interactions. These loci should beevaluated in other germplasms to determine whether allelic variation at the QTLexists in other breeds.