Abstract This paper describes the application of an expert system to the determination of planning applications in respect of the landslide hazard prevalent in South Wales. The system models a geotechnical assessment made by a senior engineer and the knowledge elicitation process is briefly described. Applications are processed via one of three knowledge bases which relate to: sites remote from documented landslides; sites in close proximity to documented landslides; and sites on documented landslides. Planning response options have been formulated for each scenario which can be directly incorporated into the procedural framework operated by Local Planning Authorities. The system has been designed for operation by graduate engineers and geologists; it provides cost-benefits in terms of senior staff time and also provides a useful medium for staff training.