Of the three classes of bronchodilators (β2-adrenergic–receptor agonists, methylxanthines, and anticholinergic agents), the β2-adrenergic–receptor agonists produce the greatest bronchodilation in patients with bronchial asthma.1 β2-Adrenergic agonists are generally preferred both for the relief of acute symptoms2,3 and for the prevention of exercise-induced bronchospasm.4 The recent introduction of long-acting inhaled β2-adrenergic agonists has overcome the principal shortcoming of the previously available drugs of this class, their limited duration of action. However, the possibility of adverse effects with regular use of β2-adrenergic agonists has been raised.5–7 In this article I . . .