Bronchodilators are central in symptomatic management of all stages of COPD. For patients whose COPD is not sufficiently controlled by monotherapy, combining an inhaled anticholinergic and a ss(2)-agonist is a convenient way of delivering treatment and obtaining better lung function and improved symptoms. Formoterol (beta(2)-agonist) and tiotropium (anticholinergic) are long-acting bronchodilators with different mechanisms of action. Formoterol has a fast onset and a bronchodilator effect of approximately 12 h, while tiotropium has a 24-h bronchodilator effect and is given once daily. Currently, there is no documentation that tiotropium is superior to formoterol or the contrary, but a combination of tiotropium and formoterol is more effective than single drugs alone in inducing bronchodilation and a bronchodilator-mediated symptom benefit in patients suffering from COPD. Once-daily or twice-daily formoterol, added to tiotropium, are both better than tiotropium alone, but the published evidence suggests twice-daily formoterol is the best add-on option.