Studies have been conducted in the USA comparing fluticasone propionate aqueous nasal spray 200 mu g once daily with beclomethasone dipropionate aqueous nasal spray 168 mu g twice daily, oral terfenadine 60 mg twice daily, or oral astemizole 10 mg once daily given for 2 or 4 weeks during tree, grass or ragweed pollen seasons. All six were multicentre, randomised, placebo-controlled, double-blind, parallel-group studies. Efficacy was evaluated by patient and clinician assessments of individual nasal symptoms and overall response to therapy. Fluticasone propionate was superior to beclomethasone dipropionate in one trial according to patient evaluations of symptoms, but response to fluticasone propionate and beclomethasone dipropionate was similar in the second study. Comparisons with antihistamines showed fluticasone propionate to have greater efficacy. It was more effective than terfenadine in both trials according to evaluations by clinicians and patients. Similar findings were observed in the first astemizole trial. The second astemizole study showed superiority of fluticasone propionate over astemizole in terms of patient and clinician evaluations of overall response to therapy and occasionally in terms of symptom evaluations. There were no significant adverse effects, including effects on plasma cortisol concentrations, noted in any of these comparator studies.