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with an overall mean of 692 and 49 ng/m3 for inhalable and respirable fractions, respectively. Endotoxin concen-tration was usually higher in the day than at night. These concentrations give cause for concern for the health of stockmen working in such buildings. The corresponding mean emission rates from poultry houses were 678 and 43 lg/h (500 kg) liveweight, respectively, 51 and 6 lg/h (500 kg) liveweight from pig buildings and 9 and 1 lg/h (500 kg) liveweight from cattle houses. A new automated bioaerosol sampler was developed, which allows remote, independent sampling of airborne microorganisms. Its principle of operation is similar to a slit sampler: airborne microbes are collected by impac-tion on an agar surface. Most measurements of airborne The air in intensive livestock buildings usually con-tains high concentrations of airborne microorganisms.1–4 Normally, these microorganisms are associated with dust particles and present a biologically active aerosol (bio-aerosol). They can cause or trigger lung-related diseases in animals and man,5–7 while many common pathogens of pigs and poultry are known to be transmitted aerially.8 Some non-pathogenic microbes, e.g. the genus Micro-coccaceae, can become opportunistic pathogens under certain conditions, such as poor air quality which can interfere with respiratory defence mechanisms. Fungi and their specific mycotoxins are also important, especiall