Much information science research has focused on the design of systems enabling users to access, communicate, and use information quickly and efficiently. However the users’ ability to exploit this information is seriously limited by finite human cognitive resources. In cognitive psychology, the role of attentional processes in allocating cognitive resources has been demonstrated to be crucial. Attention is often defined as the set of processes guiding the selection of the environmental stimuli to be attended. Access to information therefore is not only regulated by its availability but also by the users’ choice to attend the information—this choice being governed by attentional processes. Recently several researchers and practitioners in Human Computer Interaction (HCI) have concentrated on the design of systems capable of adapting to, and supporting, human attentional processes. These systems, that often rely on very different technologies and theories, and that are designed for a range of applications, are called attention-aware systems (AAS). In the literature, these systems have also been referred to as Attentive User Interfaces (Vertegaal, 2003). However, we prefer using the former name as it stresses the fact that issues related to attention are relevant to the design of the system as a whole rather than limited to the interface. The recent interest in this field is testified by the publication of special issues in academic journals (e.g., Communication of the ACM, 46(3), 2003; International Journal of Human-Computer Studies, 58(5), 2003) and by the organisation of specialised fora of discussion (e.g., the workshop on “Designing for Attention”; Roda & Thomas, 2004). In this article, we discuss the rationale for AASs and their role within current HCI research, we briefly review current research in AASs, and we highlight some open questions for their design.