The primary aim of this study was to investigate whether previous findings ofsimilar quantitative trait loci (QTL) positions for correlated yield traits aredue to a pleiotropic QTL. We applied a multitrait variance component based QTLmapping method to a dataset involving five granddaughter families from theGerman Holstein dairy cattle population. The marker map contained 16microsatellite markers, distributed across chromosome BTA6. A chromosomewisesignificance threshold was used, because BTA6 is known to harbor QTL for severalmilk traits. To evaluate the results from the multivariate, across-familyanalysis, we also conducted single-family analyses using the least squaresmethod of QTL estimation. The results provided two significant QTL findings at49 and 64 cM for milk yield in different families and putative QTL at 68 cM forfat yield and at 71 cM for protein yield in another family. The results for fatand protein yield were confirmed by a univariate, across-family variancecomponents analysis. The multivariate analysis of three bivariate traitcombinations resulted in a significant pleiotropic QTL finding at 68 cM for fatyield and protein yield, bracketed by markers TGLA37 and FBN13. The estimates ofvariance contribution due to this QTL were 23% and 25%, respectively.