In our aim to characterize the genetic background of variation in pork quality traits as well as to examine the possibilities of including quantitative trait loci (QTLs) in a marker assisted selection scheme, we have performed a QTL study in large half-sib families. The quality traits included ultimate pH in longissimus dorsi and the semimembranosus, drip loss, and the Minolta color measurements, L*, a* and b* representing meat lightness, redness and yellowness, respectively. The families consist of 3,883 progenies of 12 Duroc boars that were evaluated to identify the QTLs. The linkage map consists of 462 SNP markers on 18 porcine autosomes. QTLs were mapped using a linear mixed model with fixed factors: sire, sex, herd, month, sow-age and, random factors: polygenic effect, QTL effects and litter. Chromosome-wide and genome-wide significance thresholds were determined by Peipho's approach, and 95% Bayes credibility intervals were estimated from a posterior distribution of the QTL position. In total, 31 QTLs for the six meat quality traits were found to be significant at the 5% chromosome-wide level, among which 11 QTLs were significant at the 5% genome-wide level and 5 of these were significant at the 0.1% genome-wide level. Segregation of the identified QTLs in different families was also investigated. Most of the identified QTLs segregated in one or two families. For the QTLs affecting ultimate pH in longissimus dorsi and semimembranosus and L* and b* value on SSC6 the positions of the QTLs and the shapes of the likelihood curves were nearly the same. In addition, a strong correlation of the estimated effects of these QTLs was found between the four traits, indicating that the same genes control these traits. A similar pattern was seen on SSC15 for the QTLs affecting ultimate pH in the two muscles and drip loss. The results from this study will be helpful for fine mapping and identifying genes affecting meat quality traits, and tightly linked markers may be incorporated into marker assisted selection programs.