['Proinflammatory mediators such as the cysteinyl leukotrienes are important in the pathophysiology of allergic rhinitis. This study evaluated the efficacy and tolerability of montelukast, a cysteinyl leukotriene receptor antagonist, given once daily in the morning for treatment of seasonal (fall) allergic rhinitis for 4 weeks.', 'This was a randomized, double-blind trial with a placebo run-in and a 4-week treatment period. Patients (n = 1079) with a history of allergic rhinitis and a positive skin test to seasonal pollen allergens were assigned to placebo, montelukast 10 mg, or loratadine 10 mg. Symptoms were assessed with a daily diary.', "Montelukast was more effective than placebo in improving scores for the primary endpoint of daytime nasal symptoms (P = 0.003) and the secondary endpoints of night-time, composite, and daytime eye symptoms, patient's and physician's global evaluations of allergic rhinitis, and rhinoconjunctivitis quality-of-life (P </= 0.006). The positive control loratadine also improved scores for the primary endpoint (P </= 0.001) and the majority of the secondary endpoints (P < 0.03). When analyzed by week, the treatment effect of montelukast was more persistent than loratadine over all 4 weeks of treatment."] Does montelukast improve symptoms of seasonal allergic rhinitis over a 4-week treatment period?