This book is open access under a CC BY-NC 2.5 license.The book aims to be a resource for those interested in planning and implementing large-scale information infrastructures for novel electronic services in health care. The focus of this book is on the pivotal role of the installed base (i.e. the already existing elements of an infrastructure) for ensuing infrastructural development. The book presents rich empirical cases on the design, development and implementation of core infrastructural components (e-prescription and public patient-oriented web platforms) in different national settings across Europe. Therefore, this is a book in which theoretical insights and practical experiences are tightly connected. Contributions have been sourced from a network of academics that have been working on the topic for years, and who have previously collaborated and shared a common understanding of the challenges entailed in expanding information infrastructures within healthcare.