Recently, Geographical Information System (GIS) has emerged as an innovative and important component of many projects in public health and epidemiology. One of the most useful functions of GIS in epidemiology continues to be its utility in basic mapping. GIS may also involve more sophisticated spatial analysis of disease occurrence and contributing environmental factors. Depending on the quantity and quality of data and the methodology used in analysis, a given map may be either useful or misleading. Although visual analyses (mapped evidence) strengthened by exploratory analyses are mostly sufficient for epidemiologists, the formal testing of certain hypotheses or the estimation of relationships between measures of disease incidence and, for example, environmental covariates require quantitative modelling of disease distribution. It is a promising prospect that spatial statistics and GIS technology have slowly started to merge. However, whether GIS will be useful in the model-based approach and the prediction in, for example, epidemiology remains to be seen. The desired future development of GIS requires a switch of emphasis from data and information to knowledge.