Two aspects of the social psychology of collective action are of particular interest to social movement organizers and activists: how to motivate people to engage in collective action, and how to use collective action to create social change. The second question remains almost untouched within social psychology. The present article delineates research from political science and sociology concerning variables that moderate the effectiveness of collective action and maps these variables against intergroup research. Within intergroup social psychology, there is a theoretical literature on what needs to be done to achieve change (e.g., changing identification, social norms, or perceptions of legitimacy, stability, permeability). The article considers possible testable hypotheses concerning the outcomes of collective action which can be derived from intergroup research and from the synthesis of the three disciplines. For theoreticians and practitioners alike, a program of research which addresses the social-psychological outcomes of collective action and links these to identities, norms, intentions, and support for social change in bystanders, protagonists, and opponents has a great deal of interest.