Asthma varies in severity over time; consequently, treatment regimens must be sufficiently flexible to be adjusted when necessary. At present, inhaled corticosteroids (ICS) remain the cornerstone of asthma therapy and optimal treatment strategies must consider total daily dose and dosing frequency. The dose responsiveness to ICS varies for different indices of asthma. Symptoms and lung function respond readily to low-dose ICS and the dose-response curve is relatively flat. In contrast, the prevention of asthma exacerbations displays a more pronounced dose-response relationship. In mild asthma, once-daily dosing with budesonide is as effective as twice-daily dosing. However, in moderate-to-severe asthma, four-times daily dosing is better than twice-daily dosing for obtaining maximal benefit with minimal side effects. A flexible treatment regimen, consisting of lowdose maintenance treatment combined with high dose and frequently dosed ICS at the earliest sign of an exacerbation, has been shown to be effective. This could be achieved using a single inhaler combination product if the beta(2)-agonist moiety allows for the same flexibility in dosing. Formoterol, with its wide dose range, rapid onset and long duration of effect, has the pharmacological features that permit this versatile, flexible dosing. As a result, Symbicort((R)) would seem to offer the flexibility required in a single inhaler for maintenance and reliever purposes in the management of this variable disease. (C) 2002 Elsevier Science Ltd. All rights reserved.