This course examines the consequences of ethnic heterogeneity for political competition and conflict around the world. The course is organized into four sections. The first section of the course introduces alternative theories of how ethnic groups form and how identification with ethnic groups may influence social and political behavior. The second section of the course investigates the effect of ethnic group membership on electoral competition across polities with a wide variety of demographic, economic, and institutional characteristics. In this part of the course, we will examine such questions as what conditions make ethnicity salient in electoral contests and does the saliency of ethnicity influence the stability of democratic regimes. The third section of the course evaluates the consequences of ethnic heterogeneity for policymaking and economic performance in democratic societies. We will analyze the effect of ethnic divisions on redistributive policymaking, public goods provision, and economic growth. The fourth and final section of the course investigates whether ethnic heterogeneity in a polity affects the incidence of political violence including riots, civil war, and terrorism. In this section of the course, we will also evaluate the effectiveness of a number of common policy interventions for reducing ethnic conflict.