Background: The combination of fluticasone furoate (FF), a novel inhaled corticosteroid (ICS), and vilanterol (VI), a long-acting β2 agonist, is under development as a once-daily treatment of asthma and COPD. The aim of this study was to compare the efficacy of FF/VI with fluticasone propionate (FP)/salmeterol (SAL) in patients with persistent asthma uncontrolled on a medium dose of ICS. Methods: In a randomized, double-blind, double-dummy, parallel group study, 806 patients received FF/VI (100/25 μg, n = 403) once daily in the evening delivered through ELLIPTA (GlaxoSmithKline) dry powder inhaler, or FP/SAL (250/50 μg, n = 403) bid through DISKUS/ACCUHALER (GlaxoSmithKline). The primary efficacy measure was 0- to 24-h serial weighted mean (wm) FEV 1 after 24 weeks of treatment. Results: Improvements from baseline in 0- to 24-h wmFEV 1 were observed with both FF/VI (341 mL) and FP/SAL (377 mL); the adjusted mean treatment difference was not statistically significant (-37 mL; 95% CI, -88 to 15, P = 0.162). There were no differences between 0- to 4-h serial wmFEV1, trough FEV1, and asthma control and quality-of-life questionnaire scores. There was no difference in reported exacerbations between treatments. Both treatments were well tolerated, with no clinically relevant effect on urinary cortisol excretion or vital signs and no treatment-related serious adverse events. Conclusions: The efficacy of once-daily FF/VI was similar to bid FP/SAL in improving lung function in patients with persistent asthma. No safety issues were identified. © 2013 American College of Chest Physicians.