Intermedia is a hypermedia system developed for use in university research and teaching. It provides a framework for object-oriented, direct-manipulation editors and applications, and the capability to link materials created with those applications. Instructors are able to construct explanatory environments for their students as well as use applications for their day-to-day work, research, and writing. A general discussion of hypermedia is followed by a description of the Intermedia system. The description focuses on several important user-interface features and illustrates the operation of the system through a sample session. It is shown how object-oriented programming techniques and a complementary set of software development tools helped programmers work together and maintain a consistent user-interface throughout the system