The aim of this study was to compare the efficacy and safety of salmeterol/fluticasone propionate combination product (SFC) with fluticasone propionate (FP) plus oral montelukast (M) over 12 weeks in symptomatic asthma patients. The study was a multinational, randomised, double-blind, double-dummy, parallel-group design in patients aged ≥15 years. After a 4-week run-in during which all patients received FP 100 μg twice daily, patients were randomised to inhaled SFC (50/100 μg) twice daily or inhaled FP 100 μg twice daily and oral M 10 mg once daily. Patients kept daily records of their peak expiratory flow (PEF), symptom scores and use of rescue medication. Over the 12-week treatment period, the adjusted increase in mean morning PEF was significantly greater in the SFC group (36 l/min) than the FP/M group (19 l/min;P <0.001). The improvement in FEV₁ was also significantly greater in the SFC group (mean treatment difference 0.11 l; P<0.001). SFC provided significantly better control of daytime and night-time symptoms and there were fewer exacerbations. Patients in the SFC group were also significantly more likely to have a rescue-free day. Both treatments were equally well tolerated. Combination therapy with FP plus salmeterol (SFC) produced significantly greater improvements in lung function and asthma control than the addition of montelukast to FP.