The coadministration of long-acting inhaled beta2-agonists and inhaled corticosteroids is the most effective treatment for persistent asthma. It is often assumed that there is synergy between these medications. Many studied mostly extensively as a maintenance therapy for patients with persistent asthma, the combination inhaler is at least equivalent to its components administered separately and is superior to monotherapy with salmeterol/formoterol or inhaled corticosteroid in both pediatric and adult populations. The combination has a logical role in the treatment of moderate-to-severe asthma, offering the advantage of increased convenience and possibly improved compliance. In addition to improvements in lung function, symptom scores and quality of life, the combination therapy reduces exacerbation rates, an outcome that contributes to favorable cost-effectiveness.