▪ Abstract Given the global trend of increasing ethnocultural diversity and the outbreak of nationalist movements based on cultural, linguistic, and territorial identities, this review focuses on social and political mechanisms that lead to the emergence of minority group collective action. This kind of collective action is seen as a function of three necessary conditions: the formation of distinctive social identities, the overcoming of free riding, and the development of institutional structures promoting the demand for greater autonomy. The article examines the debates, theories, and empirical evidence concerning these three conditions. We conclude by noting that the most important impediment to progress in this field is the relative paucity of historical and cross-national databases that are required to test many of the theories in the literature.