Administrative silence, also known as formal inactivity of the administration, is an important topic in the field of comparative administrative law and has gained recognition in many legal systems around the world. It is seen as a necessary tool for the protection of individual rights and, in many jurisdictions, it is considered a constitutional guarantee that citizens have against the powers of administrative authorities. Many international human rights treaties impose a duty on these authorities to respond to citizens' petitions. However, when there is a failure in this duty by an administrative authority, there is a requirement to determine how this has happened and the consequences of this failure.This book provides an overview of the concept of administrative silence, its importance in protecting individual rights, and explores how it is recognised and applied within 21 jurisdictions around the word. It is a useful reference for anyone interested in the subject and it aims to improve knowledge on the topic and gives it the attention that it deserves within the framework of comparative administrative law.