This book constitutes the joint thoroughly refereed post-proceedings of the 9th IFIP International Conference on Engineering for Human Computer Interaction and of the 11th International Workshop on Design, Specification, and Verification of Interactive Systems, EHCI-DSVIS 2004, held in Hamburg, Germany in July 2004.The 25 revised full papers presented have gone through two rounds of reviewing and improvement and were selected from initially 65 submissions. The papers are organized in topical sections on usability, task modeling, browsing and searching, model-based approaches, ubiquitous computing, bridging viewpoints, plastic and adaptive interfaces, and groupware.