OBJECTIVE To determine whether montelukast is as effective as fluticasone in controlling mild persistent asthma as determined by rescue-free days. METHODS Participants aged 15 to 85 years with mild persistent asthma (n = 400) were randomized to oral montelukast (10 mg once nightly) or inhaled fluticasone (88 mug twice daily) in a year-long, parallel-group, multicenter study with a 12-week, double-blind period, followed by a 36-week, open-label period. RESULTS The mean percentage of rescue-free days was similar between treatments after 12 weeks (fluticasone: 74.9%, montelukast: 73.1%; difference = 1.8%, 95% confidence interval [CI]: -3.2% to 6.8%) but not during the open-label period (fluticasone: 77.3%, montelukast: 71.1%; difference = 6.2%, 95% CI: 0.8% to 11.7%). Although both fluticasone and montelukast significantly improved symptoms, quality of life, and symptom-free days during both treatment periods, greater improvements occurred with fluticasone in lung function during both periods and in asthma control during open-label treatment. Post hoc analyses revealed a difference in rescue-free days favoring fluticasone in participants in the quartiles for lowest lung function and greatest albuterol use at baseline. CONCLUSIONS In patients with mild persistent asthma, rescue-free days and most asthma control measures improved similarly with fluticasone or montelukast over the short term, but with prolonged open-label treatment, asthma control improved more with fluticasone. Improved asthma control with fluticasone appeared to occur in those with decreased lung function and greater albuterol use at baseline. In the remaining patients, the two treatments appeared to be comparable. These results suggest that classification criteria for mild persistent asthma may need to be re-evaluated.