Hypertext is being used more and more often for on-line course texts. However, the navigational freedom offered by a rich link structure is a burden for students who need guidance throughout the learning process. This paper presents a framework for adaptive link structures. By enabling links when a student is ready to read the pages these links lead to, and disabling links to pages that are no longer needed, the student can be assured that links always lead to interesting new information she is ready to read. This framework is illustrated by means of the courseware for an on-line course on ‘Hypermedia structures and systems’, developed at the Eindhoven University of Technology.