Previous research on gender and sports has focused on the ways women athletes emphasize their femininity to counter critics who conflate female athleticism with mannishness and lesbianism. My findings from an ethnographic study of three roller derby leagues suggest that many "rollergirls" view their hyper-feminine, sexualized uniforms as a playful and pleasurable expression of their sexual agency, not as a means to prove their femininity or heterosexuality. By combining these uniforms with a full-contact sport, rollergirls attempt to "undo gender" by actively resisting the gender binary that equates athleticism and toughness with masculinity. Yet my findings also illustrate the importance of considering the social context in which these performances take place. While rollergirls assert that wearing sexualized, feminine uniforms is a "choice," others feel pressured to dress "sexy" in order to attract fans. In addition, their uniforms sometimes lead to unwanted attention from some men in the crowd who misinterpret the intended meanings of their self-presentation. This research emphasizes the importance of understanding women’s individual feelings of agency in the context of social inequality.