The anti-inflammatory effects of drugs can be studied non invasively using sputum which has either been produced spontaneously or induced with hypertonic saline. We have developed an efficient semi-automated method to examine sputum which should be widely applicable. This approach is recommended to provide a direct sampling of the airway secretions to study the inflammatory process and to demonstrate drug effects. We have validated a method to prospectively induce a mild exacerbation of airway inflammation by controlled reduction of inhaled steroid in steroid-dependent asthmatics. This can be used to examine the ability of drugs to prevent or reverse airway inflammation.