Although many forms of differential treatment based on group membership are perceived to be legitimate, disadvantaged group members' responses to discrimina-tion have been studied primarily in contexts in which such treatment is appraised as illegitimate. This has resulted in an impoverished understanding of differential group-based treatment and a failure to illuminate the processes by which discrimi-nation can shift from being seen as legitimate to being viewed as illegitimate. We discuss the determinants of disadvantaged group members' legitimacy appraisals and the de-legitimisation process, whereby forms of discrimination appraised as legitimate come to be increasingly perceived as illegitimate. Whether group-based exclusion is addressed collectively or individually depends on socio-structural factors such as the pervasiveness of discrimination, impermeability of intergroup boundaries, and the availability of cognitive alternatives to the status quo. We conclude that understanding the antecedents and consequences of legitimacy appraisals is necessary to develop a comprehensive account of disadvantaged group members' experiences of group-based discrimination. Virginia Woolf begins her 1929 book, A Room of One's Own, by recollecting an incident that occurred on the university campus of "Oxbridge". She describes how, when she attempted to visit the university library, she was stopped at the door and was not allowed to enter. The doorman told her that "ladies are only admitted to the library if accompanied by a Fellow of the College or furnished with a letter of introduction" (p. 9). At that moment Woolf did not challenge Correspondence should be addressed to Jolanda Jetten,