Social psychological research is increasingly coming to grips with the complexity of social identity within the individual, both from the perspective of perceivers trying to form impressions and make judgments about multiply categorizable targets, as well as from the perspective of actors using their different self-aspects as a framework for guiding their interactions with the social world. I review several contributions to the effort to better understand these issues and then explore some of their possible implications for understanding the nature and consequences of diversity within the group. The importance of social categories in guiding social cognition and behavior was recognized decades ago by seminal figures in social psychology (Allport, 1954;Sherif, 1948;Tajfel, 1974). Since then, research on social categorization and associated phenomena such as stereotyping and intergroup conflict has flowed in a steadily increasing stream, attesting to the theoretical centrality and practical significance of these issues. Much of the social psychological research that has been conducted in this tradition has focused on one identity dimension at a time (e.g., race or sex or nationality) and has assumed the existence of distinct, discrete categories within a given dimension (e.g., clearly defined racial groups) rather than overlapping, blended, or ambiguous categories. In addition, researchers often tend either to adopt the perspective of the observer, asking how social categories are imposed on target persons in the course of social perception, or they adopt the perspective of the actor, asking how categorical identities are claimed or disavowed in the course of self-perception, and how these identities influence subsequent selfregulation. These research traditions have yielded undeniably rich and diverse insights into the dynamics of social categorization, but the picture they have produced has not fully come to terms with some of the inherent complexities of social categorization.In recent times, researchers have begun to turn their attention more explicitly toward the multifaceted nature of social identities. The diversity of identity, within the individual, has been increasingly recognized and investigated, both from the perceiver's and the actor's perspectives. The impact of a group's diversity on group dynamics and productivity has also been increasingly recognized in recent years, but the issue becomes more complicated when one recognizes the diversity that resides within the individual members comprising the group. In this article, I review some of the recent research and theory bearing on the diversity of identity, considering its implications both for individuals and groups. As will become clear, many key issues remain ripe for empirical exploration.