Background: Antihistamines effectively treat seasonal allergic rhinitis (SAR), although the ability of this drug class to reduce nasal congestion is limited. Nasal decongestants effectively treat nasal congestion but not the histamine-related components of SAR. Therefore antihistamine/nasal decongestant combinations are commonly used to maximize the treatment of SAR, Fexofenadine HCl is a nonsedating, long-acting H-1 receptor antagonist that provides fast and effective relief from SAR. It is well tolerated, with no sedative or cardiotoxic effects. Objective: We sought to compare the efficacy and safety of a fexofenadine HCl/pseudoephedrine HCl combination with that of each individual component in the treatment of ragweed allergy, Methods: In this Canadian multicenter, double-blind, parallel-group study, 651 patients allergic to ragweed were randomized to receive 60 mg of fexofenadine HCl twice daily, 120 mg of sustained-release pseudoephedrine HCl twice daily, or a combination of the 2 drugs (60 mg of fexofenadine HCl/120 mg of sustained-release pseudoephedrine HCl) twice daily for 2 weeks, Efficacy analyses were based on symptom severity. In addition, a health economic assessment was performed, Results: Combination therapy was significantly more effective than pseudoephedrine alone in improving primarily histamine-mediated symptoms (sneezing; rhinorrhea; itchy nose, palate, and/or throat; and itchy, watery, red ea es) and significantly more effective than fexofenadine alone in reducing nasal congestion. Combination therapy also produced greater improvements in daily activities and work productivity compared with the individual components. No serious adverse events were reported in any of the treatment groups. In addition, no clinically significant changes in 12-lead electrocardiogram parameters, vital signs, or clinical laboratory values were observed. Conclusion: Combination therapy is more effective than fexofenadine alone or pseudoephedrine alone in relieving the full spectrum of SAR symptoms tie, both the primarily histamine-related symptoms and nasal congestion).