A F2 population derived from a cross between European Large White and ChineseMeishan pigs was established in order to study the genetic basis of breeddifferences for growth and fat traits. Chromosome 4 was chosen for initial studyas previous work had revealed quantitative trait loci (QTLs) on this chromosomeaffected growth and fat traits in a Wild Boar x Large White cross. Individualsin the F2 population were typed for nine markers spanning a region ofapproximately 124 CM. We found evidence for QTLs affecting growth betweenweaning and the end of test (additive effect: 43.4 g/day) and fat depth measuredin the mid-back position (additive effect: 1.82 mm). There was no evidence ofinteractions between the QTLs and sex, grandparents or F1 sires, suggesting thatthe detected QTLs were fixed for alternative alleles in the Meishan and LargeWhite breeds. Comparison of locations suggests that these QTLs could be the sameas those found in the Wild Boar x Large White cross.