Enterprise architecture is an important instrument to address company-wide integration both from a business and an IT point of view. Companies that choose to implement an Enterprise Architecture initiative often believe that if a description of the company’s architecture exists it will automatically generate value to the company but sadly, this is usually not the case. Even if companies know that enterprise architecture is important they still have problems with modelling and management of the enterprise architecture. The purpose of this article is two fold, to describe how an Enterprise Architecture is established and to identify the critical factors that affect the modelling and management of the Enterprise Architecture. The research is based on empirical study of two different companies: AstraZeneca and SKF. Both companies have several years of experience working with enterprise architectures and represent two completely different branches. The critical factors found are grouped in three different areas: Management, Scope and Content. To succeed with an enterprise architecture initiative it requires top IT and business management buy-in. The scope of the enterprise architecture must be defined and agreed between business and IT. To make the enterprise architecture useful the content must have certain characteristics. To get the buy-in of the business community the business functions and processes must be included and described with relevant artefacts and in business terminology in line with the scope.