This edited volume is the first endeavour to systematically investigate the role of trust in the different relations within regulatory regimes. Trust as a multifaceted concept is contested within public administration and political science in general and especially within the relation between regulator and regulated party. The aim of this book is to scope the field and to set the agenda for further research. In this introductory chapter we map the different relations within regulatory regimes and review empirical research into the role of trust within the different relations. Our review reveals several themes that we address in the different empirical chapters and in the research agenda formulated in the concluding chapter.