This paper investigates the pedagogical basis of Adaptive Educational Hypermedia Systems (AEHS) that incorporate Learning Styles in order to accommodate user’s learning style preferences and needs. Therefore, AES adapt the learning content, its presentation and navigation to the user’s learning style preferences. We collect thirty three (33) Adaptive and Intelligent Web-based Educational Systems (AIWBES) that incorporate learning styles and discuss twenty of them, namely the AEHS, as the remaining are Intelligent Tutorng Systems. The main achievement of this work is the investigation of AEHS’ pedagogical basis in terms of adaptation rules. We conclude that these systems follow similar patterns in their adaptation logic.