In sport horses, the breeding goal of many stubooks is focused on performance at the highest level of competition in dressage and show-jumping. There is a tendency among practical breeders to specialise towards one of these two disciplines, although some
breeders still aim at breeding a so-called dual purpose horse. The general goal of this thesis was to provide useful information for the breeding programme of the Royal Dutch Warmblood Studbook (KWPN) in relation with the ongoing specialisation of the population. In this thesis, we analysed the effect of specialisation on the genetic links between the subpopulations of dressage and show-jumping horses of KWPN population, and the impact of the specialisation on the genetic parameters of traits measured in both subpopulations. Finally, we estimated the genetic correlations between disciplines as well as between disciplines and traits measured in the studbook-entry inspections. Based on the findings from these studies we concluded that a breeding programme under specialisation is most effective when it comprises separate aggregate breeding goals for each of the disciplines, rather than one combined breeding goal.