Statistical problems are described which arose in the attempt to estimate the overall extent and cost of farm accidents in Great Britain. Information was obtained on all 56 fatal accidents and on a sample of 791 non-fatal accidents reported to the Health and Safety Executive between 1 July 1981 and 30 June 1982. Consideration is given to the planning and execution of a survey of 805 farms to obtain information on unreported accidents. Difficulties in deriving national estimates and problems of communicating results are also covered. 1.1 Background The modernisation and particularly mechanisation of farming in Britain has exposed farmers and farm workers to health and safety risks which are greater than those faced by workers in other industries. Not only has agriculture become increasingly mechan- ised, but machines are now larger and more powerful, and there has been a growth in the use and variety of toxic chemicals, such as pesticides. Furthermore, a steadily declining labour force (with less than half of all farms now employing non-family labour) and an increase in the speed and sophistication of many operations have meant that workers are often alone and unsupervised for long hours. The necessity to operate an extensive range of specialist equipment, much of which may be used for short periods only but requiring the acquisition of particular operating skills, has created further risk to users. The use of pesticides, aerial spraying and straw burning represent potential hazards to the farming and rural community. There are additional health hazards specific to farm work, particularly tetanus, farmer's lung and Weil's disease. A distressing component of the farm accident record is the fatal and serious injuries sustained by children, reflecting the circumstances of the 'family farm' and the proximity of home and workplace. The available data on farm accidents have largely been limited to fatal accidents and those non-fatal accidents which are reported to the U.K. Health and Safety Executive (HSE): until 1983 these were mostly accidents to employees for which Industrial Injury Benefit was claimed. Little information is available, however, on non-fatal accidents to employees for which state benefits are not claimed, nor on those sustained by self-employed persons (who now exceed employees in farming) not entitled to benefits. In addition to the compelling humanitarian reasons for making agriculture a safer and healthier environment in which to live and work, there are economic reasons for pursuing health and safety improvement. Accidents cost money and resources; to the injured party, to the employer, to the National Exchequer and to the national