Administration of dust mite by inhalation is considered investigational. However, numerous studies demonstrate the safety of allergen inhalation in well characterized subjects. A recent NHLBI/NIAID Workshop summarized evidence of the safety and utility of research bronchoprovocation and bronchoscopy studies in subjects with chronic airway diseases. Bronchoprovocation challenge has emerged as an important tool to understand the environmental factors involved in the asthmatic response. Airway hyperresponsiveness (AHR), an exaggerated bronchoconstrictor response to a variety of stimuli, is a prominent characteristic of asthma. Importantly, AHR to methacholine is correlated with symptoms and severity of disease. Although the mechanisms underlying AHR are poorly understood, it is believed to result, at least in part, from airway inflammation. Bronchoprovocation is a well-established method to detect and quantify AHR and to obtain insights into the mechanisms associated with this pathophysiologic entity. Increased airway response after allergen inhalation parallels the subsequent inflammatory reaction, suggesting that the allergen-induced inflammation has direct effects on mechanisms of airway responsiveness. Moreover, the techniques and applications of bronchoprovocation, both for testing nonspecific airway responsiveness and specific allergen challenge, have been well defined. Therefore it is evident that bronchoprovocation testing is considered useful and safe, and also likely to yield important insights into the pathogenesis of asthma.