The increase in economic disparities over the past 30 years has prompted extensive research on the causes and consequences of inequality both in the United States and, more recently, globally. This review provides an update of research on the patterns and causes of economic inequality in the United States, including inequality of earnings, wealth, and opportunity. We also explore the social and political consequences of inequality, particularly in the areas of health, education, crime, social capital, and political power. Finally, we spotlight an emerging literature on world inequality, which examines inequality trends within as well as across nations. Sociologists can advance research on inequality by bringing discipline-based expertise to bear on the organization and political economy of firms and labor markets, the pathways through which inequality has an effect, and the social, political, and cultural contingencies that might modify this effect.