This paper introduces terminology and develops a framework for incorporating and emphasizing important social and political choices that become part of the history of Computer-Based Information Systems (CBIS) and are embedded in the social structure which supports its development and use. These social and political elements of a CBIS are not just discrete elements in an environment. They can be organized in specific ways which may enhance usability and performance and, paradoxically, constrain implementations and post-implementations. It is argued argue that CBIS, developed from complex, interdependent social and technical choices are better conceptualized as institutions than as tools. The distinction between tools and institutions is important for several reasons: the usability of CBIS is the critical factor, not the technology itself; CBIS that are well-used and have stable social structures are more difficult to replace than those with less social structure and fewer participants; and CBIS vary from one social sctting to another according to the ways in which they are organized and embedded in organized social systems.