Histamine is an important chemical mediator of inflammation in asthma. The benefits of antihistamine treatment in patients with mild to moderate asthma have been well documented, however their clinical use has been previously limited due to the high doses required for efficacy and their associated side effects including sedation and cognitive impairment. Recent evidence indicates that in addition to H1-receptor antagonism, some of the newer nonsedating, non-impairing antihistamines appear to possess various anti-inflammatory properties at concentrations achieved at therapeutic dosages suggesting an additional benefit of these drugs in the management of allergic diseases and asthma. The purpose of this study is to assess the long-term safety performance of fexofenadine compared to montelukast in subjects with asthma.