Like most sport organisations, the United States Tennis Association (USTA) and Women's Tennis Association (WTA) divided participants into male and female categories. Renée Richards's very presence complicated these rules. She also surfaced just as women's tennis was making significant strides in both professional opportunities and payments. Richards's athletic career demonstrates the importance of gender norms in the determination of sex in women's tennis. She overtly challenged biological conceptions of sex but also performed stereotypical understandings of femininity. Significantly, Richards repeatedly downplayed her athleticism – to diminish concerns of her supposed biological edge – and highlighted her weakened physique. Although many argued that trans athletes threatened the sex-segregated blueprint of sport, an overview of Richards's time on the women's circuit instead illustrates a reaffirmation of binary understandings of both sex and gender. The USTA and WTA believed that Richards's biology gave her an unfair advantage in tennis.