The objective of this study was to detect quantitative trait loci on bovine chromosome 6 related to milk production parameters (milk, protein and fat yields, protein and fat contents) in Czech Fleckvieh. Breeding values for milk, protein and fat yields,protein and fat contents were taken from ice Official Database of Progeny Testing. The data evaluation was carried out by REML method using a single trait and consequently multi trait analyses. Putative quantitative trait loci affecting protein and fat contents, and then milk, protein, and fat yields were detected. In this preliminary study with lower number of animals, the significance of the loci found was not proved. However the results are a basis for larger study with higher number of Czech Fleckvieh cattle to get more accurate results.