Today, a company`s IT is challenged to support new business processes in continuously shortening cycles and to adapt to company structure or business strategy changes in a flexible way. Modern approaches like Enterprise Architecture promise to resolve the dilemma of missing IT agility by modularizing the IT landscape into reusable building blocks for flexible business process support. Service Oriented Architecture (SOA) is one possibility to implement a modular Enterprise Architecture. For an effective planning and introduction of Enterprise Architectures it is necessary to monitor and control the financial aspects on an adequate level of granularity. Since there is no mature controlling model for this kind of architecture, this book introduces a controlling model for the Enterprise Architecture, which is also applicable when adopting SOA.This book is dedicated to both - practitioners and academics - interested in the financial aspects of EAM. It is based on the results of a study conducted for Detecon International GmbH. In the meantime, the practical relevance of the developed controlling model has been proven by successful application in several consulting projects.