Airborne dust and endotoxin levels on poultry farms, were determined for various working processes known to involve a heavy exposure. Forty-seven workers at different sites were studied by questionnaires for work-related symptoms. Lung function measurements were made before and after work. Dust levels exceeded the standard for organic dust, and endotoxin levels exceeded those known to cause respiratory and other symptoms. The average decrease in FEV1 over the working day(s) ranged from 0.07-0.19 litres. Upper airway irritation was present in one third of the workers, and about 10% complained of chest tightness. The effect may have been due to the high amounts of dust causing a general respiratory irritation as well as to the endotoxin.