This supplement to CHEST, titled "Airway Hyperresponsiveness in Asthma: Its Measurement and Clinical Significance," resulted from a symposium that brought together experts from Canada, the United States, and Australia to discuss the progress in the understanding of measurements of airway hyperresponsiveness. There was an additional focus on the indirect measurement of airway inflammation and its interaction with airway hyperresponsiveness, as well as the role of measuring airway inflammation in the management of asthma.