In the early 1970s, a pilot study of farmers in Scotland found a prevalence rate of 86 cases per 1000 of the working population in some regions [40]. The incidence of acute cases in Swedish farmers has been estimated as 2–5 per 10 000 farmers per year [41,42]. According to SWORD, allergic alveolitis is the most commonly reported respiratory disorder in UK farmers, comprising 20 out of 38 notifications in farmers in 1997 [26]. By far the highest annual rates of this disease reported to SWORD (1998–2000) were in farming or veterinary jobs[4]. Because of the inconsistencies in research definitionsand the general lack of incidence data, it is difficult to identify any clear trends in the incidence of disease with time. Chronic disease can be fatal, but deaths are rare.Only 56 deaths were recorded in the UK over an 11 year period between 1979–1980 and 1982–1990 [2].Acute extrinsic allergic alveolitis can be treated with low dose oral steroids and this has been found to be as effective as avoidance of exposure. Specific preventive measures include adequate drying and conditioning of crops prior to storage, sufficient ventilation in storage facilities and use of commercial anti-mould preparations.These last contain acid-forming bacteria (commonly Lactobacillus spp.), the products of which inhibit mould growth. General measures to reduce organic dust levels are mentioned later. Avoidance of allergens is usually recommended to prevent chronic lung damage, although some studies have shown that those who experience the disease and remain in farming have comparable long term pulmonary function to those who leave the industry[43]. Thus, change of occupation may not be necessary,although affected workers should be encouraged to avoid certain activities (e.g. cleaning barns, silos, grain bins, etc.) to minimize contact with mouldy hay, grain or straw and to use respirators for high-risk activities.