This paper considers whether transgender women should be permitted to compete in female categories in sports. Trans* women are often criticized for competing in female categories because they are seen as having an unfair advantage. Specifically, they are seen as having high levels of testosterone that unfairly enhance their performance in comparison to cisgender competitors. In this paper, I argue that trans* women should be permitted to compete in female categories. I suggest that if we want to maintain the skill (...) thesis as a guiding principle of sports and allow trans* women to compete in female categories, then we need to take relevant genetic advantages into consideration by introducing a handicap system. I claim that a handicap system should consider both cisgender and transgender women’s effective testosterone levels. (shrink)