With growing interest in the analysis of the geographical distribution of disease this book serves as an introduction to the field. It provides a practical guide to the basic concepts of "spatial epidemiology" and "disease mapping". It includes up-to-date information in the area, illustrated with numerous examples. Interest in the analysis of the geographical distribution of disease has recently gathered pace. A variety of factors have contributed to this level of interest. Growing public awareness of environmental hazards has led to an increased demand for public health authorities to investigate geographical clustering of diseases. Although such cluster analyisis is nearly always ineffective in identifying causes of disease, it often has to be used to address public concern about environmental hazards. Interpreting the resulting data is not always straightforward, however, and this volume presents a guide to the non-specialist. The pitfalls include the fact that cluster analyses are usually done post hoc, and not as a result of a prior hypothesis. This is particularly true for investigations prompted by reported clusters, which have the inherent danger of over estimating the disease rate through "boundary shrinkage" of the population from which the cases are assumed to have arisen.