The experiment aimed at studying gene expression differences in longissimus dorsi muscle from pigs from two groups: High versus low intramuscular fat (IMF). The animals were selected from a crossbred population of Landrace x Yorkshire/Landrace x Duroc animals, where we have previously found a highly significant QTL for IMF (Grindflek et al. 2001: "Detection of quantitative trait loci for meat quality in a commercial slaughter pig cross", Mammalian Genome 12(4): 299-304), and by microarray analysis we hoped to identify candidate genes for the QTL and/or pathways that are affected by the genes responsible for the QTL. Keywords: phenotype comparison Overall design: Direct dye-swap design, with 14 animals in each group (high IMF and low IMF) on 14 separate arrays