As web sites continue to grow in their complexity, one of the most important usability design decisions is how to structure the web site topic hierarchy. This decision lays the groundwork for designing other aspects of the site, e.g., the home page table of contents, and for categorizing new documents in the topic structure over the life of the site. Organizing web sites is a timely topic as evidenced by the recent spate of publications on this topic [1] [2] [3] and by NIST's recent release of a tool, WebCAT, to help users participate in organizing their web site. More significantly, the organization is probably the limiting factor on success for web sites that provide useful information.If anything is clear about the organization of web sites, it is that there is no single best way to go about it. Different types of web sites seem to demand different approaches to organization. For example, a site geared toward product support might use a task-oriented scheme that steps users through a process of problem-solving. Other sites, such as an online shopping site, might be organized according to categories of products, in order to allow efficient browsing. Other sites might be organized based on an analysis of user roles.Designers who must choose among these schemes must also choose appropriate analyses to inform the design of the web site structure. These include item clustering techniques, user performance at finding documents using various prototype web site organizations, studies of user roles and tasks, and analyses of the material to be included in the site.