This paper explores the potential for geographical information system technology in defining some variables influencing the use of primary care medical services. Eighteen general practices in Scotland contributed to a study examining the accessibility of their services and their patients' use of the local Accident and Emergency Department. Geo-referencing of information was carried out through analysis of postcode data relating to practices and patients. This information was analyzed using ARC/INFO GIS software in conjunction with the ORACLE relational database and 1991 census information. The results demonstrate that GIS technology has an important role in defining and analyzing the use of health services by the population.