The quality of the user interface has a great bearing on the utility of a geographic information system. The user interface, however, has not been a strong point of GIS. To increase the efficiency of GIS the user interface must provide a simple conceptual model of what is happening to the database. It must be easy to learn, appear natural, and independent of implementation complexities such as data structures and algorithms. In order to do this, the user interface of the GIS should show itself to its user as a system, and not as various collections of data. This paper discusses how traditional user interface design focuses on how to best represent the software functionality rather than on how to meet the expectations of the user. User-Centered Design is offered as an alternative that focuses on the two-way mapping between system functionality and the user's conceptual model of the system. Graphical user interface techniques are discussed as ways of creating the necessary two way mapping and facilitating the usability of GIS systems.