In some patients, asthma control is improved by combining inhaled corticosteroids with long-acting beta(2)-agonists. However, fluctuating asthma control and exacerbations can still occur. The STAY study evaluated whether, in patients with moderate to severe asthma, replacing a short-acting beta(2)-agonist reliever with the combination of budesonide/formoterol as reliever would both provide rapid symptom relief and reduce asthma exacerbations. The study evaluated 2760 patients with asthma (4-80 years) randomized to budesonide 400 microg twice daily (bid) and terbutaline as reliever, budesonide/formoterol 100/6 microg bid and terbutaline as reliever, or budesonide/formoterol 100/6 microg bid both as maintenance and reliever. Children (age 4-11 years) used a once-daily maintenance dose. Budesonide/formoterol as maintenance and reliever significantly reduced severe exacerbation risk by 45% to 47% compared with the other 2 treatments and improved symptoms, awakenings, and lung function. The benefit was seen in patients of all ages. Subsequent studies have revealed that this beneficial effect of budesonide/formoterol as maintenance and reliever requires both components of the combination.