Scholars have developed an increasingly rich set of research findings regarding the structure of political networks. Network approaches ahve shed new light on the connections among political candidates, donors, and interest groups; legal precedents, opinions, and jurists; terrorist groups; and actors engaged in weapons trading. As other chapters in this volume attest, networks such as these affect a wide range of political outcomes. For example, political attitudes and behavior can be shaped by the individuals in their social networks, legislative behavior can be influenced by the formal and informal ties that connect legislation, decision-making by political officials can reflect the policy networks with which they are affiliated, and political regimes can be responsive to the structure of interstate relations. Studying the ways in which influence is transmitted through political networks has enriched our theories of political outcomes in all fields of political science.