The chapters in this volume build upon the social identity theory-based assumption that people create a social self. They utilize information about the groups to which they belong to inform their sense of themselves, shaping their social selves in terms of those categories that are salient in group divisions (social categorization). Having differentiated the world into categories, people then judge their worth as individuals, at least in part, through the favourability of the status of the groups to which they belong. The nine chapters are organized into three sections. The first focus primarily on general issues of theory. They each suggest elaborations or extensions of the social identity and self-categorization approaches to studying the social self. The second is based on the assumption that the social self exists and elaborates its nature and functions. The third explores the influence of social context upon the social self. Together, these chapters demonstrate the vitality and heuristic utility of social identity theory for social psychology. The authors have extended their social identity analysis to a wide variety of issues. Their approaches are linked to a core assumption that groups are important to individuals not only because they allow them to exchange resources with others, but because groups also provide individuals with important information that is used to construct the social self. Hence, social groups exist within individuals because they define an important aspect of the self. They do so both by defining the dimensions through which people categorize the world and by providing the valance through which people’s position along those dimensions is evaluated. The authors argue that this core assumption provides the framework for the creative study of a wide variety of aspects of the self and social interaction.