A QTL analysis of fat androstenone levels from a three-generation experimentalcross between Large White and Meishan pig breeds was carried out. A total of 485F2 males grouped in 24 full-sib families, their 29 parents and 12 grandparentswere typed for 137 markers distributed over the entire porcine genome. The F2male population was measured for fat androstenone levels at 100, 120, 140, and160 d of age and at slaughter around 80 kg liveweight. Statistical analyses wereperformed using two interval mapping methods: a line-cross (LC) regressionmethod, which assumes alternative alleles are fixed in founder lines, and ahalf- full-sib (HFS) maximum likelihood method, where allele substitutioneffects were estimated within each half- and full-sib family. Both methodsrevealed genomewide significant gene effects on chromosomes 3, 7, and 14. TheQTL explained, respectively, 7 to 11%, 11 to 15%, and 6 to 8% of phenotypicvariance. Three additional significant QTL explaining 4 to 7% of variance weredetected on chromosomes 4 and 9 using LC method and on chromosome 6 using HFSmethod. Suggestive QTL were also obtained on chromosomes 2, 10, 11, 13, and 18.Meishan alleles were associated with higher androstenone levels, except onchromosomes 7, 10, and 13, although 10 and 13 additive effects were near zero.The QTL had essentially additive effects, except on chromosomes 4, 10, and 13.No evidence of linked QTL or imprinting effects on androstenone concentrationcould be found across the entire porcine genome. The steroid chromosome P45021-hydroxylase (CYP21) and cytochrome P450 cholesterol side chain cleavagesubfamily XIA (CYP11A) loci were investigated as possible candidate genes forthe chromosome 7 QTL. No mutation of coding sequence has been found for CYP21.Involvement of a candidate regulatory mutation of CYP11A gene proposed by otherscan be excluded in our animals.