Asthma is a disease that is, in large part, defined by abnormalities of pulmonary function. Failure of any new treatment modality to improve objective measures of lung function suggests a limited usefulness of such new therapies. The clear dissociation between inflammation and airways responsiveness indicates the latter is not solely dependent on the former. Recent long-term treatment trials suggest that monitoring the degree of airways responsiveness, and returning responsiveness toward a normal value should be an obtainable goal of therapy. The effects of large inhalations and loss of lung volume dependence suggest that linkage between the airways and lung parenchyma are a key to maintenance of airway patency. Measurement of lung function remains the most practical means for the assessment of permanent changes in lung structure. New developments in monitoring lung function, especially using forced oscillation approaches, show particular promise in assessing the lung function of the asthmatic person.