It is now 25 years since the publication of Tajfel and Turner's (1979) seminal statement on social identity theory and 15 years since Ashforth and Mael (1989) published their classic Academy of Management Review article pointing to the potential value of using this theory to enhance researchers' understanding of organizational life. Whatever else the latter article may have achieved, it is clear that it was highly prophetic, as, over the intervening period, industrial and organizational psychologists' interest in social identity and related concepts has increased at a phenomenal rate. On top of nearly 300 citations of the Ashforth and Mael paper, this is indicated, among other developments, by the publication of several key books and journal special issues devoted to research in this area (e.g.,