Current understanding defines asthma as an inflammatory disease. However, recent evidence suggests that the inflammatory process extends beyond the central airways to the most distal parts of the lungs, to the small peripheral airways and the lung parenchyma. The difficulty in measuring changes in the small airways due to the lack of specificity and sensitivity of pulmonary function tests has resulted in the considerable under-estimation of the role of these airways in asthma. Moreover, the low resistance of the small airways means that severe damage and obstruction can occur in these airways before symptoms occur. Thus inflammation at this site is a key feature of the pathogenesis of asthma. Therefore, treatment of asthma should be directed to both the large and small airways to achieve maximal suppression of inflammation throughout the airways. Leukotriene receptor antagonists and anti-IgE monoclonal antibodies are examples of such therapies.