This article analyzes the postwar transformation of the Dutch Warmblood farm horse into a riding horse. It gives special attention to the farmers’ practical breeding methods and to the role that scientists and government policymakers played in the transformation process. Until the 1970s, Warmblood breeding methods were a continuation of pre-Mendelian methods that focused on qualitative assessment of a horse’s conformation, that is, its exterior characteristics. In 1980, the Dutch government undertook an effort to modernize Warmblood breeding by turning it into a collectively organized, scientific enterprise. These plans were largely subverted by the fierce opposition of breeders. Nevertheless, quantitative scientific methods, particularly quantitative genetics, started to make inroads into Warmblood breeding at the time. However, the breeders’ decision to switch to quantitative methods was a reaction to other pressures, economic and otherwise, rather than a response to the government’s call for science-based modernization. Moreover, qualitative assessment remained as important in the selection of breeding stock as before.