In this paper, we present an Adaptive Educational Hypermedia (AEH) based on Case Based Reasoning (CBR) approach and XML language. CBR may be very useful in e-Learning technologies. It should be viewed as a medium to be used in conjunction with the majority shared information system. In this context, we think that a standard way of marking up cases will facilitate this use. We suggest XML as the likely candidate to provide such standard. XML is used in order to represent the domain model, the user model and the case in the CBR system. CBR is used to simplify the process of personalization by reusing previous experiences.