The aim of this study was to assess the prevalence of asthma (selfreported) and relate this to lung function and factors associated with asthma in young farmers.Two hundred and ten female and 1,691 male farming students together with 407 males controls were studied. Each subject underwent a medical interview; forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were recorded using a dry wedge spirometer. Histamine bronchial reactivity was measured using the Yan method. Skin prick testing was performed using inhalant allergens.Nonsmokers had lower prevalence of asthma (5.4±10.8%) than smokers (11.3± 21.0%) (p<0.05). Females reported symptoms of asthma nearly twice as often as males. Sex, smoking and a family history of asthma/allergy were significantly associated with asthma. Controls had higher standardized FEV1 and FVC residuals than male students, both nonsmokers (0.21 and 0.24) versus (-0.06 and -0.05) and smokers (0.29 and 0.33) versus (-0.11 and 0.13) (p<0.032). Bronchial hyperresponsiveness, asthma, siblings with allergy and working with cattle (controls only) were significantly associated with reduced lung function.In conclusion, the prevalence of asthma was significantly related to smoking, female sex, family history of asthma and allergy. Whilst bronchial hyperresponsiveness was associated with reduced lung function and lung function was slightly reduced in the male farming students, there was no association found between occupational farming exposure and either lung symptoms or lung function. Eur Respir J 1999; 13: 31±37. Exposure to fumes and both organic and inorganic dusts represents an occupational hazard in farming. High concentrations of carbon dioxide, hydrogen sulphide and ammonia have been measured inside animal confinement buildings [1±4]. Analyses of the dust have revealed several compounds including animal-derived material such as dander, hair, saliva and urine [5,6], bacteria [7,8], endotoxin [7,9,10], fungi [8,11], spores [9,12] and mites [13,14]. Inhalation of these substances might result in cellular and immunological responses that could lead to lung diseases.The prevalence of asthma in farming populations, studied in the northern part of Europe, has shown a range 2.1± 32% [15±18]. Positive skin prick test [15], pig farming [16] and positive test to both storage and house dust mites [17] have been suggested as risk factors for asthma, and exposure to dusts, animals and fodder yeast have been reported as provoking factors for asthma in the farming population [18].The influence of occupational exposure on lung function in agricultural workers has been studied in farmers working in dairy barns and mainly in swine confinement buildings. Most of the studies have been cross-sectional [19, 21±30] but some longitudinal studies have been published [20,29,32]. Dairy farming has been found to be associated with minor lung function changes both in the UK [19] (forced expiratory volume in one second (FEV1)) and in Finland [20] (forced vital capacity (FVC)). In s...