We established realness as the relatively stable tendency to act on the outside the way one feels on the inside, without regard for proximal personal or social consequences. In nine studies, we showed that realness is a) a core feature of individual differences in authenticity, b) generally adaptive but largely unrelated to agreeableness, c) highly stable, d) reliably observable in dyadic behavior, and e) predictive of responses to situations with potential for personal or social costs. Informants both perceive agreeable motives in real behavior and recognize that being real can be disagreeable. We concluded that realness represents an important individual difference construct that is foundational for authentic social behavior, and that being real comes with both costs and benefits.