Printed in Great Britain The use of mapping in public health and planning health services

The availability of relatively inexpensive, user-friendly geo-graphical information systems, with a steadily extending range of analytic and other facilities, provides a powerful tool for the analysis and display of the increasing number of health-related data sets, and for their greater accessibility. Relationships between several sets of variables can become immediately apparent from a map in a way that is much more difficult to comprehend from a table or description. It is also easy to define ad hoc areas, such as the area adjacent to a possible toxic point source or to a main road, in terms of unit postcodes and Census output areas, to determine standar-dized rates for mortality and hospital admissions. Apart from the geographical information system itself, the basic require-ments are access to relevant data sets including Census data, and to the central postcode directory, which provides grid references for unit postcodes and permits matching of postcoded health events to Census output areas