There are good statistics for deaths in transport accidents, fires, and from accidents in the home in Great Britain, and considerable (but less comprehensive) information about injuries and material damage. Information about the causes of these events is much more scanty, and little is known about the long-term effects of accidental injury. The available data are reviewed and the nature, magnitude and frequency of various kinds of risks are analysed for different age groups and in relation to environmental and other factors. The contribution of 'voluntary' actions (notably alcohol and smoking) is assessed. Finally, the extent to which both actual and perceived risk can be modified by education, engineering (modifying the design of roads, vehicles, aircraft, homes and fittings), and the enforcement of regulations and control systems is evaluated. While costs cannot easily be measured, false perceptions of risk can lead to wasteful investment, and education and information are essential if resources are to be deployed where they will do most good.