This paper suggests that the stories that thoroughbred breeders tell about racehorse reproduction can contribute to an understanding of their ideas about relatedness between humans. It examines the thoroughbred pedigree as it is presented in the English sales catalogue as a locus of complex ideas about heredity, fertility, and procreation. It argues that resistance within the industry to new reproductive technologies, including artificial insemination, can be understood in terms of ideas about relatedness between horses and, by implication, between people.This paper (...) is based upon extensive participant observation conducted within the horseracing industry based in the town of Newmarket, England. (shrink)