Quantitative trait loci (QTL) for fatness traits were reported recently in anexperimental Meishan x Large White and Landrace F(2) cross. To furtherinvestigate the regions on pig Chr 2 (SSC2), SSC4, and SSC7, 25 additionalmarkers from these regions were typed on 800 animals (619 F(2) animals, theirF(1) parents, and F(0) grandfathers). Compared with the published maps, amodified order of markers was observed for SSC4 and SSC7. QTL analyses wereperformed both within the half-sib families as well as across families (linecross). Furthermore, a QTL model accounting for imprinting effects was tested.Information content could be increased considerably on all three chromosomes.Evidence for the backfat thickness QTL on SSC7 was increased, and the locationcould be reduced to a 33-cM confidence interval. The QTL for intramuscular faton SSC4 could not be detected in this half-sib analysis, whereas under the linecross model a suggestive QTL on a different position on SSC4 was detected. ForSSC2, in the half-sib analysis, a suggestive QTL for backfat thickness wasdetected with the best position at 26 cM. Imprinting analysis, however, revealeda genome-wise, significant, paternally expressed QTL on SSC2 with the bestposition at 63 cM. Our results suggest that this QTL is different from thepreviously reported paternally expressed QTL for muscle mass and fat depositionon the distal tip of SSC2p.