Abstract. Interactive digital television is an emerging field with a high impact in our societies: it offers interactive services to the masses. This tutorial aims to establish a common framework by summarizing the most significant results in this multidisciplinary field. The review includes topics such as content distribution, system software of the receivers, and user interaction. In addition, we will discuss current commercial events such as the next generation of optical discs (e.g., blue-ray), BBC peer-to-peer service, and mobile television. Based on this discussion, we will formulate an agenda for further research. The agenda includes, for example, end-user enrichment of television content and social television. This half-day tutorial will provide the attendee a solid understanding of the technologies currently in use and an introduction of the open questions in the field.