In the past, the accepted method of plan making was to survey the area, analyse its problems, and produce a plan which described a state of affairs expected at some future date. The new theories adopted a continuous, cyclical systems approach based on the identification of needs and goals, the formulation and evaluation of alternative cources of actions and monitoring of adopted programmes. This process clearly requires planning to improved its ability to use information system. In Malaysia, changes to the planning legislation favour the new approach. However, there is no adequate information system to aid the process. The implications of using Geographical Information Systems for planning at the municipal level are examined in this study, initially, with reference to Kuala Lumpur as a whole but more specifically, with reference to a detailed case study of planning for the management of squatter problems. After the initial development of the GIS database, it is used to evaluate the existing characteristics of the Jinjang/Kepong Squtter Settlement. Subsequently, a number of scenarios are developed which take into accountthe socio-economic characteristics of the squatters, the constraints of the physical layout of existing squatter settlements, availability of land and site suitability for different kinds of developement. Spatial modelling techniques are employed to examine alternative plans for the squatter areas. These plans are evaluated using cost-benefit analysis incorporated into the GIS for the case study is the development of an interactive graphic user interface for squatter planning and management. This utilises the ARC/INFO Arc Macro Language (AML) to aid user access to alternative planning scenarios. The interface provides flexibility in data selection and display, to allow physical planners and decision-makers to view and analyse the planning scenarious interactively, before deciding on the final plan. The final part of the thesis highlights some of the problems encountered in the case study and indicates factors which need to be considered if GIS is to be employed in this type of exercise. Data requirements, problems of data availability, the appropriateness of different analytical tools are examined. This is followed by a discussion of the feedback between the information system and the planning/decision-making process which is necessary for the successful implementation of new GIS technology in a developing country.