A number of studies have already demonstrated the clinical effectiveness of formoterol when used as maintenance therapy in patients requiring both a β₂-agonist with a long duration of action and a regular inhaled corticosteroid. However, formoterol has a unique mechanism of action that gives it both fast- and long-acting properties. Hence the question arises as to whether formoterol can also be used as first-line reliever medication in addition to maintenance therapy. Compared with terbutaline, formoterol used as needed in steroid-treated mild to moderate asthma has superior efficacy, not only significantly improving peak flow, but also the exacerbation rate. In moderate to severe asthma, formoterol used as needed has demonstrated efficacy comparable with salbutamol and terbutaline in improving symptoms and lung function. Single doses of formoterol have also been shown to result in protection against exercise-induced bronchoconstriction for periods up to 12 h. Furthermore, bronchoprotection was maintained following repeated dosing, although further research is needed to confirm the duration of protection achieved with frequent and regular use. Initial research also suggests that formoterol is as effective and well tolerated as terbutaline in the treatment of acute asthma attacks. The evidence presented supports the use of formoterol on an as-needed basis for effective asthma control.