Asthma is a chronic inflammatory disease of the airways characterised by circadian and episodic symptoms, including wheezing, breathlessness, chest tightness and/or cough. It is one of the most common chronic diseases in adults and children, affecting approximately 15 million people in the US alone. Asthma is associated with considerable direct costs (e.g. hospitalisation, emergency care and drug therapy) and indirect costs (e.g. loss of income, loss of school days and premature death).Patient education and objective parameters of assessment are important aspects of asthma management. With the recognition of the need to reduce the underlying airways inflammation, the regular use of anti-inflammatory drugs [e.g. inhaled corticosteroids, nedocromil or sodium cromoglycate (cromolyn sodium)] is currently recommended for prophylaxis of asthma. Inhaled short-acting bronchodilators are used intermittently for relief of acute asthma symptoms.Salmeterol is a long-acting inhaled&bgr;2-agonist that produces significant bronchodilation and protects against asthma induced by a number of broncho-constricting stimuli (including exercise) for at least 12 hours. In clinical trials of up to 12 months' duration in patients with mild to moderate asthma, inhaled salmeterol 50&mgr;g twice daily was more effective than short-acting inhaled&bgr;2-agonists [salbutamol (albuterol) and terbutaline] in improving lung function, alleviating symptoms and reducing the requirement for additional inhaled salbutamol. Salmeterol was at least as effective as sustained-release theophylline in controlling nocturnal asthma symptoms. Recent studies have shown that addition of salmeterol to existing low dosage inhaled corticosteroid therapy is more beneficial than increasing the dosage of inhaled corticosteroids in patients with inadequate control of asthma symptoms. Salmeterol has been well tolerated in clinical trials and there is no convincing evidence to suggest that long term use of salmeterol increases asthma morbidity or mortality. Regular use of long-acting&bgr;2-agonists such as salmeterol may result in some decreased protection against induced bronchoconstriction, but clinically significant tachyphylaxis to broncho-dilatory response has not been demonstrated.It is important to emphasise that inhaled long-acting&bgr;2-agonists, including salmeterol, should be used in conjunction with, and not as a replacement for, oral or inhaled corticosteroids. Long-acting&bgr;2-agonists should always be used in conjunction with anti-inflammatory drugs (and short-acting&bgr;2-agonists for symptom relief).In conclusion, available data and recommendations from recent UK and US asthma guidelines suggest that inhaled salmeterol is effective in preventing exercise-induced asthma and, when added to low dose inhaled corticosteroids, is a useful alternative to increasing the inhaled corticosteroid dosage for long term control of symptoms (especially those occurring at night).