This chapter describes literature about IT investments, and the impact of IT on the performance of a firm. The reason for this study is that effects of IT standards, which are an integral part of IT, will be investigated in several case studies. Supporting the case study analysis, a method will be adopted that is used to assess business performance from IT in general. Business performance in general can be assessed from different angles, such as financial performance, process performance and transaction performance. Literature from various disciplines shows the complexity of and the disagreement as regards measurement and description of business performance. However, it is generally accepted that these impacts can be assessed best at the intermediate level: that of business processes. After the introduction, literature dealing with IT value and business performance will be discussed. Then a specific method, the Balanced Scorecard, will be dealt with and an explanation is given why we used it in this research. This chapter concludes with a look at the concept of flexibility, as part of business performance, and what it means in relation to IT standards.