Over the last two decades, EU legislation has established a growing number of subsidiary bodies commonly referred to as EU decentralised agencies. Recent years have witnessed the conferral of increasingly significant powers to these bodies to the point where the successful implementation of many of the EU's policies is now dependent upon the activities of EU agencies. While EU agencies have become indispensable in terms of their practical importance, the lack of a legal basis in the EU Treaties to establish and empower new bodies as well as the lack of an adequate framework in secondary law means that there exists little control over EU agencies. This results in critical issues, such as the absence of clear criteria prescribing when an agency may be empowered to act and also the failure to consider the interests of the actors normally responsible for the implementation of EU law, such as the Member States and the Commission. Providing the first comprehensive overview of the development of agencification in the EU, this book explores the question: What are the political and legal limits to EU agencification? Analysing EU agencies from an institutional and constitutional perspective, the book traces the development of EU agencies, explores the different tasks they perform, investigates the limits to agencification, and discusses the legal basis for such agencies.