The aim of the work reported is to support regional planning tasks by providing co-workers who are situated at different locations with access to a GIS. Five technical challenges for application sharing are identified: multiple views, multi-user access, feedback about other users activities, conference management facilities and sustainable performance. A system is presented which re-uses an existing single-user GIS and encompasses a User Interface Management System (UIMS), knowledge-based techniques and agent support for group-work. This novel approach offers a solution to the technical challenges, while enhancing the usability of such systems.