This book examines administrative silence in a comparative manner in the EU law and 13 jurisdictions from Europe. Administrative silence is an issue that lies at the intersection of legal and managerial aspects of public administration, a concept that is both reflecting and testing the principles of legal certainty, legality, good administration, legitimate expectations, and effectiveness. Inactivity or excessive length of proceedings appears to be of interest for comparisons, particularly in the context of the recent attempts to develop European convergence models. The book offers in-depth insights into legal regulation, theory, case law and practice regarding positive and negative legal fictions in the selected European jurisdictions.