ABSTRACT The study is tracing testosterone through debates and regulations of participation in women’s elite sport between 2015 and 2022. We are interested in the ways that testosterone becomes an agent in constructing sport-bodies as gendered bodies and sustaining as well as deconstructing binary gender categories in elite sport. Furthermore, taking up feminist science and technology studies, affect and trans theory, we are interested in what testosterone does to the ways elite women athletes are imagined, but moreover, we are interested in the figures and signifiers that get attached to testosterone within elite sporting realms, such as questions of fairness and danger. Based on a dataset of documents, regulations, and press releases from a range of international sports organizations and articles from Danish media debates on (especially trans) women’s participation in sports, we analyse selected cases of woman athletes, sport organization and sport disciplines that have been involved in debates about testosterone rules and levels in women’s sport.