We provide a research agenda for the International Cartographic Association's Commission on Visualization and Virtual Environment Working Group on Cognitive and Usability Issues in Geovisualization. Developments in hardware and software have led to (and will continue to stimulate) numerous novel methods for visualizing geospatial data. It is our belief that these novel methods will be of little use if they are not developed within a theoretical cognitive framework and iteratively tested using usability engineering principles. We argue that cognitive and usability issues should be considered in the context of six major research themes: 1) geospatial virtual environments (GeoVEs); 2) dynamic representations (including animated and interactive maps); 3) metaphors and schemata in user interface design; 4) individual and group differences; 5) collaborative geovisualization; and 6) evaluating the effectiveness of geovisualization methods. A key point underlying our use of theoretical cognitive principles is that traditional cognitive theory for static two-dimensional maps may not be applicable to interactive three-dimensional immersive GeoVEs and dynamic representations—thus new cognitive theory may need to be developed. Usability engineering extends beyond the traditional cartographic practice of "user testing" by evaluating software effectiveness throughout a lifecycle (including design, development, and deployment). Applying usability engineering to geovisualization, however, may be problematic because of the novelty of geovisualization and the associated difficulty of defining the nature of users and their tasks. Tackling the research themes is likely to require an interdisciplinary effort involving geographic information scientists, cognitive scientists, usability engineers, computer scientists, and others.