Geoinformatic systems are sociotechnical systems for sensing, modeling, representing, visualizing, monitoring, processing, and communicating geoinformation in support of urban and regional planning and design and similar activities. Geoinformatics is the technological and scientific discipline guiding the design of such systems. In this paper, which is based on a recent Swedish research program, geoinformatic systems are discussed from the viewpoint of the profes­ sional regional and urban planner. The main deficiencies with current technical planning support are identified and a comprehensive set of user requirements and specifications for a planning support system and a planning environment is presented.