Several years we began a new trend in the Advances in Group Processes series. Our goal then was to publish a set of five interrelated volumes that examine core issues or fundamental themes in the group processes arena. Each volume was to be organized around a particular problem, substantive area, or topic of study, broadly defined to include a range of methodological and theoretical orientations. Volume 22 represents the fourth volume in the series, addressing fundamental issues of Social Identification in Groups .