BACKGROUND Traditional clinical outcomes have demonstrated that salmeterol improves pulmonary function and reduces asthma symptoms. However, they do not evaluate how patients perceive the effect of therapeutic intervention on day-to-day functioning and well-being. OBJECTIVE We sought to evaluate the impact of salmeterol on disease-specific quality of life with the Asthma Quality-of-Life Questionnaire, as well as the efficacy and safety of salmeterol in patients with stable asthma who were symptomatic despite daily use of inhaled corticosteroids. METHODS This was a randomized, double-blind, placebo-controlled, parallel-group study of 506 patients. Patients were treated with 42 microg salmeterol or placebo twice daily for 12 weeks delivered through a metered dose inhaler. RESULTS Mean change from baseline in asthma quality-of-life scores was significantly greater (p < or = 0.006) after 12 weeks of treatment with salmeterol compared with placebo ("as-needed" albuterol) in global scores (1.08 vs 0.61) and individual domains (activity limitations, 0.91 vs 0.54; asthma symptoms, 1.28 vs 0.71; emotional function, 1.17 vs 0.65; and environmental exposure, 0.84 vs 0.47). Patients treated with salmeterol experienced significantly greater improvements from baseline to week 12 compared with placebo in FEV1 (0.42 L vs 0.15 L, p < 0.001), morning peak expiratory flow (47 L/min vs 14 L/min, p < 0.001), evening peak expiratory flow (29 L/min vs 11 L/min, p < 0.001), and asthma symptom scores (daytime scores reduced by 0.55 vs 0.30, p < 0.001). Patients treated with salmeterol used significantly less supplemental albuterol (reduced by 3 puffs/day vs 1 puff/day, p < 0.001). CONCLUSIONS Salmeterol provided significantly greater improvement in quality-of-life outcomes in patients whose asthma symptoms are not well controlled with inhaled corticosteroids. These results demonstrate that the benefits of salmeterol are not limited to conventional clinical measures of efficacy.