Architectures and tools are two important considerations in the construction of interactive computer systems. The former is concerned with the optimal structural organisation of systems and the latter with the effective support of the design and management of user interfaces. They are regarded as the areas of research most likely to contribute to the development of existing interactive systems, in particular by providing improved architectures capable of supporting new styles of interaction and more sophisticated software tools to improve productivity. This volume combines the proceedings of two workshops held in York and Glasgow which concentrated on architectures and tools respectively. In doing so it addresses the problems of user interface construction from two complementary viewpoints and provides alternative perspectives on many of the central issues. Some of the papers are published in expanded form to provide a more comprehensive coverage of the topics and two additional papers have been included which offer a useful insight into issues raised by the workshops. The papers address formal and theoretical concerns as well as academic and commercial ones. Specific topics covered include novel-input models, architectures for real-time systems and object-oriented user interface tools for X-widgets, NeWS- and Smalltalk-based applications. The papers also include presentations of new tools and architectural designs. Building Interactive Systems: Architectures and Tools provides the most extensive recent account of research into the relationship between architectures and tools in the construction of interactive computer systems and will be of interest to researchers, postgraduate students and software developers.