Disease mapping is the usual means of presenting descriptive geographic data on disease occurrence and creating accurate maps of disease morbidity and mortality. Maps convey instant visual information on the spatial distribution of disease and can identify subtle patterns which may be missed in tabular presentations. The purpose is to display variations in ill-health (for example, related to the underlying sociodemography), formulate etiologic hypotheses, aid surveillance to detect areas of high disease incidence, and help place specific disease.