BACKGROUND We compared the efficacy and tolerability of the intranasal corticosteroid fluticasone propionate with that of the antihistamine terfenadine in patients with seasonal allergic rhinitis. METHODS Two hundred thirty-two adults and adolescents with seasonal allergic rhinitis received intranasal fluticasone propionate (200 micrograms once daily), terfenadine tablets (60 mg twice daily), or placebo for 2 weeks in a double-blind, randomized, parallel-group study. Main outcome measures were clinician- and patient-rated individual and total nasal symptom scores (based on ratings of nasal obstruction, sneezing, nasal itching, and rhinorrhea); clinician-rated overall response to therapy; changes in nasal inflammatory cell counts; adverse events; and morning plasma cortisol concentrations. RESULTS Both clinician- and patient-rated total and individual nasal symptom scores were significantly lower in the fluticasone group than in either the terfenadine group or the placebo group at nearly every measured time point throughout the treatment period. After 2 weeks of therapy, clinician-rated total nasal symptom scores decreased by 49% in the fluticasone group compared with 27% in the terfenadine group and 19% in the placebo group. In general, therapy with terfenadine was not statistically distinguishable from that with placebo based on patient-rated total or individual nasal symptom scores. According to clinician ratings, 64% of fluticasone-treated patients compared with 49% and 44% of patients treated with terfenadine and placebo, respectively, experienced significant or moderate improvement. A greater percentage of fluticasone-treated patients compared with either terfenadine- or placebo-treated patients experienced reductions in intranasal eosinophil and basophil counts after 2 weeks of therapy. No unusual or serious drug-related adverse events were reported. Morning plasma cortisol concentrations after 2 weeks of therapy did not differ among groups. CONCLUSIONS Fluticasone aqueous nasal spray, a well-tolerated corticosteroid preparation that can be administered once daily, is more effective than terfenadine tablets or placebo in controlling symptoms of seasonal allergic rhinitis.