Designing for and researching interactivity within many computer-mediated environments – from digital libraries to consumer shopping and distance education – has consumed our interest for the past decades. While research has focused on the functional aspects of interaction and support for the user’s task, a repeated complaint is that little empirical research exists about the concept of engagement, and how it should be measured. Engaging systems are more likely to grab user interests while ‘hiding’ the aspects of the system to ensure intuitive, non-intrusive, ‘invisible’ design. This research is the beginning of a larger project to determine: how do users become engaged in computer-mediated environments? How is engagement sustained? What factors influence disengagement? In this paper, we propose a model of engagement, not as a single instance or point in time, but as an ongoing process – a sequence of events during user-system interaction.