We look at the life cycle of an enterprise information system in a company. In the following chapters, we delve into four topics: the selection and implementation of standard business software, its adaption (customization), access control, and system administration. According to the perspective of the book, viz., that of a company using the enterprise information system, our life cycle begins after the “birth,” i.e., the development of the enterprise information system by the software vendor. Its development is therefore not in focus, but some aspects can be found in the “in-house development” part of the chapter on customization.