Respiratory diseases have long been recognized in association with work in farming. Overall, only a small proportion of the population is employed in agriculture, so respiratory disease in farmers is not a major public health issue. However, farmers are known to have high morbidity and mortality from certain respiratory diseases, as shown by routinely collected statistics. Despite this, knowledge of the frequency, nature and risk factors for some respiratory disorders in agricultural workers is incomplete. Multiple exposures are common and some exposures can give rise to more than one specific disease. Moreover, the most common respiratory symptoms reported by farm workers (wheeze, dyspnoea and cough) are relatively non-specific and can be associated with several occupational respiratory disorders. This review describes the main occupational respiratory illnesses in farming and summarizes the current literature about epidemiology and prevention. The most important diseases are rhinitis and asthma, which, although common, are not usually fatal. Some non-allergic conditions, e.g. asthma-like syndrome and organic toxic dust syndrome, are not yet fully understood, but appear to be common among farm workers. The most serious respiratory diseases are hypersensitivity pneumonitis and respiratory infections, but these are rare. Most importantly, respiratory diseases are preventable by controlling harmful exposures to organic dust, toxic gases and chemicals on farms through improvements in animal rearing techniques, ventilation of animal accommodation, careful drying and storage of animal feed-stuffs, crops and other products, and use of personal protective equipment.