The social construction of geographical information system (GIS) technology requires two-way relationships between technology and people. GIS technology, like any other technology, is more than a tool; it connects different social groups in the construction of new localized social arrangements. We examine several instances of how GIS technology involves social negotiation by using a construct of boundary objects developed in a social constructivist framework. Much like geographic boundaries, boundary objects separate different social groups at the same time that they delineate important points of reference between them. Boundary objects stabilize relationships through the negotiation of flexible and dynamic coherences. The negotiation of differences between different groups is fundamental to the construction of GIS technology. Social-constructivist theories and the concept of boundary objects open new ways to understand the relationships between technology and people. We illustrate the application of boundary object theory through studies of the use of GIS data standards and the definition of wetlands.