Crucial to understanding the behavior of judges and the outputs of courts is the institutional context in which they operate. One key component of courts' institutional structure is that the judiciary system is organized as a hierarchy, which creates both problems and opportunities for judges. In this essay I evaluate the literature on several features of the judicial hierarchy. I focus on core issues addressed by political scientists, legal scholars, and economists, including such questions as why hierarchy exists; how higher courts can best oversee lower courts; how learning takes place both within and across the levels of the judiciary; and how collegiality influences judicial decision making. I conclude with thoughts on potential future theoretical and empirical avenues for furthering our understanding of the importance of the judicial hierarchy.