During the last decades a process of specialization has occurred into show jumping (JH) and dressage (DH) in the Dutch Warmblood studbook (KWPN). As a consequence, the genetic base might become stratified. The objective of this study was to estimate the connectedness between JH and DH subpopulations of the current generation. The material comprised horses that participated in the studbook entry inspections between 2005 and 2010. KWPN is registering jumping and dressage horses using different codes since 2005. Ancestors were traced back as far as possible in the pedigree to define the base generation. Subsequently the base generation was divided into 3 base groups, according to having only descendants in JH, in DH or in both subpopulations. Subsequently, the genetic contribution of the 3 base groups to the subpopulations was estimated. DMUTRACE software was used to make the pedigrees files and to calculate the genetic contributions. The base generation comprised 8205 horses, 2 857 only had descendants in JH, 1893 only in DH and 3455 in both subpopulations. The latter base-group also had the largest contributions to both subpopulations: 92.6% to JH and 96.0% to DH. The “specialist” base groups had smaller genetic contributions but 47.8% of horses in JH and 34.1% in DH receive genes from them. Observed by year of birth, the number of horses that received genes from specialist groups increased from 39.8 to 56.0 % in JH and from 31.9 to 39.5 % in DH. Results from this study show that JH and DH subpopulations have a large part of their genetic base in common. However, an increasing percentage of animals receive genetic contributions from “specialist” genetic groups within the genetic base. This trend is more profound in the jumping discipline.