Bronchial hyperresponsiveness is a characteristic feature of respiratory diseases of the lung, including asthma and chronic obstructive pulmonary disease (COPD). However, asthmatic subjects respond to a range of physiological and chemical insults that are otherwise innocuous in healthy subjects or in patients with COPD, suggesting that the mechanisms underlying this phenomenon are characteristic of the asthma phenotype. Increasingly, there is evidence of a role for airway nerves in irritable airways and pharmacological targeting of the pathways involved may lead to the development of novel treatments for this disease. In this context, the recent cloning of the vanilloid receptor may be a useful target for drug discovery in respiratory disease.