The competitive nature of intergroup relations has been acknowledged in many contemporary views of organizations. However, there is much about the determinants of such competition that remain unclear. The primary purpose of the present chapter is to present an analysis of intergroup competition that is derived from recent social psychological research on social categorization processes and interdependent decision making in resource dilemmas. Based on this research, a general model of intergroup relations in organizations is presented. According to the model, intergroup relations are shaped by organizational factors that affect the interdependence between groups with respect to critical resources and psychological factors that affect how that interdependence is construed. The chapter draws out implications of the model with respect to such issues as the resolution of intergroup conflict, the development of intergroup cooperation, and the social nature of decision making in organizations.