This research was conducted to explore the impact of assimilation and differentiation needs on content-specific self-stereotyping. According to optimal distinctiveness theory (M. B. Brewer, 1991), social identities serve the function of satisfying individuals' need for assimilation (in-group inclusion) and their need for differentiation (distinctiveness from others). It was proposed that one of the ways optimal social identities are maintained is through self-stereotyping. In 3 studies, the needs for assimilation and differentiation were experimentally manipulated, and support was found for increased self-stereotyping in response to heightened need arousal across both self-report and behavioral measures and across different social groups. Results also demonstrated that only those participants who were highly identified with their in-group were willing to engage in negative self-stereotyping.