User interface design and development for knowledge-based systems and most other types of applications is a resource-consuming activity. Thus, many attempts have been made to automate, to certain degrees, the construction of user interfaces. Current tools for automated design of user interfaces are able to generate the static layout of an interface from the application’s data model using an intelligent program that applies design rules. These tools, however, are not capable of generating the dynamic behavior of the interface, which must be specified programmatically, and which constitutes most of the effort of interface construction. Mecano is a model-based user-interface development environment that uses a domain model to generate both the static layout and the dynamic behavior of an interface. A knowledge-based system applies sets of dialog design and layout rules to produce interfaces from the domain model. Mecano has been used successfully to completely generate the layout and the dynamic behavior of relatively large and complex, domain-specific, form- and graph-based interfaces for applications in medicine and several other domains.