|The present research examined how interactions with sexist men can trigger stereotype threat among women, undermining their engineering and mathematical performance. Chapter 1 provides an overview of the literatures on sexism and on stereotype threat. Chapter 2 validates a subtle sentence completion measure of sexism. In Chapter 3, male engineering students who scored highly on this sexism measure behaved in a dominant and sexually interested way towards an ostensible female classmate. In Chapter 4, female engineering students who interacted with such sexist men, or with confederates trained to behave in the same way, performed worse on an engineering test than women who interacted with nonsexist men. Chapter 5 conceptually replicated this finding and showed that women’s underperformance did not extend to an English test, an area in which women are not negatively stereotyped. Furthermore, interacting with sexist men lead women to suppress concerns about gender stereotypes, an established mechanism of stereotype threat. Chapter 6 discusses the implications for stereotype threat and for addressing barriers to women’s performance at school and in the workplace.