Epidemiologists investigating public heath issues are concerned with determining the prevalence, severity and prevention of a given health event. They are increasingly having to use sophisticated statistical tests to determine the significance of a clustering of a particular health event. Once a problem has been identified, the associated risk to human health can be assessed and any necessary intervention undertaken. A World Health Organisation initiative has culminated in a workshop which brought together leading experts to discuss complex methodologies for the statistical evaluation of disease mapping and risk assessment. A broad variety of the more sophisticated statistical techniques and their relevance are discussed and where appropriate examples included on putative sources of health hazards.