Gender identity reflects people’s understanding of themselves in terms of cultural definitions of female and male. In this article, we identify two traditions of research on gender identity that capture different aspects of masculine and feminine gender roles. The classic personality approach to gender identity differentiates communal from agentic traits and interests. The gender self-categorization approach comprises identification with the social category of women or men. Based on the compatibility principle, each approach should predict behaviors within the relevant content domain. Thus, personality measures likely predict communal and agentic behaviors, whereas gender self-categorization measures likely predict group-level reactions such as ingroup favoritism and outgroup derogation. Researchers have the option of using one or the other conception of gender identity, depending on their particular question of interest. Relying primarily on research conducted in the U.S., we show that both traditions provide insight into the ways that gendered self concepts link the social roles of women and men with their individual cognitions, emotions, and behaviors.