Combination products often have useful clinical benefits in asthma. The scientific rationale for combination therapy includes the fact that different agents have complimentary modes of action. Long-acting beta(2)-agonists have effects on airway smooth muscle, and inhaled corticosteroids have potent topical antiinflammatory effect. This combination has been shown to effectively reduce exacerbations and improve symptoms. Substantial clinical trial data provide a rationale for dual-control therapy supported by basic scientific data. Another combined therapy is inhaled steroids plus leukotriene-receptor antagonists, which provides the patient with two effective therapies. Leukotriene-receptor antagonist can also be combined with antihistamines for improved asthma control. Older therapies including theophylline and controlled release albuterol have been effectively added to inhaled corticosteroids, enabling a reduction in the dose of the inhaled steroids. Many other combination therapies are presently being tested.