Fluticasone Propionate Aqueous Nasal Spray (FPANS) contains a topically active glucocorticoid fluticasone propionate which has been used successfully for the treatment of seasonal allergic rhinitis. This multicentre, randomized, double-blind, double-dummy, placebo-controlled, parallel group study was designed to compare the efficacy and tolerability of FPANS with terfenadine tablets or placebo in controlling the symptoms of allergic rhinitis to grass pollen. Two hundred and fourteen patients were treated for 6 weeks during the grass pollen season with either FPANS 200 micrograms once daily, terfenadine tablets (60 mg) twice daily or placebo. Efficacy was evaluated by the analysis of symptom-free days and median symptom scores. Patients receiving FPANS had significantly more days free of nasal blockage on waking (P = 0.012) and during the day (P = 0.01) and of rhinorrhoea (P = 0.027) than those receiving terfenadine. Additionally, in terms of absolute efficacy, patients receiving FPANS demonstrated significantly more days free of the above symptoms (P = 0.017, P = 0.028, P = 0.004, respectively) and of sneezing (P < 0.001) than those receiving placebo. There were no significant differences in symptoms of nasal itching, eye symptoms, of symptoms of drowsiness between the three treatment groups. Patients in the FPANS group had significantly lower median symptom scores for nasal blockage on waking (P < 0.001) and during the day (P < 0.018) than those in the terfenadine group and significantly lower scores for nasal blockage on waking (P < 0.001), sneezing (P < 0.013) and rhinorrhoea (P = 0.005) than those in the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)