The inhaled corticosteroid fluticasone furoate (FF) and the long-acting β₂ agonist vilanterol (VI) are in development as a combined once-daily therapy for asthma and chronic obstructive pulmonary disease. Our study objectives were to compare the efficacy and safety of once-daily FF/VI with FF alone and twice-daily fluticasone propionate (FP) in patients aged ≥12 years with moderate-to-severe persistent asthma. Patients (n=586) received FF/VI 200/25 μg or FF 200 μg once-daily (evening dosing), or FP 500 μg twice-daily for 24 weeks. Co-primary end-points were change from baseline in trough forced expiratory volume in 1 s (FEV₁) weighted mean (wm) 0-24 h serial FEV1. Secondary end-points included change from baseline in percentage of rescue-free 24-h periods, percentage of symptom-free 24-h periods and total Asthma Quality of Life Questionnaire (AQLQ). Safety assessments included adverse events, 24-h urinary cortisol excretion, vital signs and ECG. FF/VI significantly improved trough FEV1 and wmFEV₁ versus FF and FP. Significantly more rescue-free and symptom-free 24-h periods were reported with FF/VI versus FF. Treatment differences for AQLQ were not significant. Incidence of adverse events was similar across groups. No clinically significant differences were seen for 24-h urinary cortisol excretion, vital signs or ECG. FF/VI resulted in statistically greater improvements in lung function and symptomatic end-points versus FF, and was well tolerated in this asthma population.