Methodologies for modeling hypermedia applications are a comparatively young, but nevertheless very promising area of current research. The rapid change of techniques and standards for the Internet, together with the explosive growth of both number and size of websites, demands a high-level conceptual framework for designing hypermedia systems. However, existing approaches focus only on information presentation, but neglect aspects like interactivity or content adaptation. This chapter presents the Hypermedia Modeling Technique (HMT), a new methodology for designing truly interactive and adaptive hypermedia applications. HMT allows to model sophisticated search interfaces offering interactive query refinement, interfaces for manipulating the underlying data source, and adaptive hypermedia documents. HMT is partly based on the Relationship Management Methodology (RMM), but has been enhanced regarding both design process and data model.