One of the most important issues in public and environmental health today concerns the type of instruments that can be used to devise quick, reliable and scientifically valid methods of rapid assessment which, in turn, can be utilized in health research and in the planning, monitoring and evaluation of health programmes. As the applications of geographical information systems (GIS) relate to the collection, storage, integration, management, retrieval, analysis and display of spatial data, it is not surprising that the potential usefulness of this new technology in the fields of health research and policy is beginning to be realized. This article seeks to demonstrate the opportunities which the use of geographical information systems can offer to research and policy on health issues. The article first describes the principles and objectives of GIS before going on to discuss hardware and software developments as well as the variety of application fields, organizations and users. Some examples of current applications are provided to illustrate the type of work being undertaken. The final sections address issues specifically related to the application of GIS in health research and policies in the European context.