Respiratory symptoms and lung function were studied in nine coffee workers who complained of job related respiratory symptoms. Six described symptoms characteristic of occupational asthma. Lung function data showed obstructive changes mostly in the smaller airways with no impairment in diffusing capacity. Bronchoprovocation testing with green coffee allergen provoked immediate asthmatic reactions with acute reductions of ventilatory capacity in four workers. The relative fall in FEF25-75% (ranging from 28% to 66%) was greater than in FEV1 (ranging from 18% to 62% of the control values). Eight of the nine workers had an increased total IgE serum level; five had positive intradermal skin tests to green coffee allergen. Most of the six healthy subjects experimentally exposed to green coffee dust in the working environment showed an acute fall in flow rates on maximum expiratory flow-volume curves. These results indicate that bronchoprovocation with green coffee allergen or green coffee dust may be used to identify subjects sensitive to green coffee.