The aim of the European Farmers' Project was to determine prevalence and risk factors of respiratory diseases in farmers across Europe. A cross-sectional study in 7 centres was carried out. In the first stage of the study, nearly 8,000 farmers in Denmark, Germany, Switzerland, the UK, and Spain answered a standardised questionnaire on farming characteristics and respiratory symptoms. The second stage of the study included exposure assessment and lung function measurements in 4 of the centres. Within the group of farmers, pig farmers were at high risk of asthma-like syndrome as compared to farmers keeping other kinds of animals. Among plant farmers, greenhouse workers were at higher risk for symptoms of asthma. The prevalence of symptoms of allergies were significantly lower among animal farmers as compared to the population of the European Community Respiratory Health Survey. In contrast, animal farmers had a significantly higher prevalence of symptoms of chronic bronchitis. The major risk factor for respiratory symptoms was shown to be ventilation of the animal houses and greenhouses. Intervention studies are now warranted to test the effectiveness of improved ventilation on respiratory health. The reasons for the low prevalence of allergic diseases among farmers are currently under study.