The most pressing problems of rapid urbanisation in Kuala Lumpur include the need for land, housing, and provision of services. The link with day-to-day planning problems, how ever, remains a critical problem. The quality of the planning and decisionmaking process can be substantially improved when valid data are appropriately and efficiently handled. The aim of this paper is to demonstrate the use of geographic information systems (GISs) in evaluating alternative solutions to squatter problems. After the initial development of the GIS database, it has been used to produce various scenarios which take into account the socioeconomic characteristics of the squatters, the constraints of the physical layout of existing squatter settlements, availability of land, and site suitability of different kinds of development. Spatial modelling techniques are employed to examine alternative plans for the squatter areas. These plans are evaluated by means of cost-benefit analysis incorporated into the GIS database. The authors also discuss the development of an interactive graphic user-interface to the GIS for squatter planning and management. This is intended to facilitate user access to squatter-planning scenarios. The interface provides flexibility in data selection and display, to allow physical planners and decision-makers to view and analyse the planning scenarios interactively before deciding on the final plan. In a concluding section some of the problems encountered are highlighted and factors which need to be considered if GIS is to be employed in this type of exercise are indicated.