Although the power of personal computers has increased 1000-fold over the past 20 years, user interfaces remain essentially the same. Innovations in HCI research, particularly novel interaction techniques, are rarely incorporated into products. In this paper I argue that the only way to significantly improve user interfaces is to shift the research focus from designing interfaces to designing interaction. This requires powerful interaction models, a better understanding of both the sensory-motor details of interaction and a broader view of interaction in the context of use. It also requires novel interaction architectures that address reinterpretability, resilience and scalability. Categories and Subject Descriptors H.5.2 [Information Interfaces and Presentation]: User Interfaces