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 investigate the efficacy and safety of fexofenadine 120mg BID compared to placebo in the treatment of subjects with mild to moderate persistent asthma.