In a single-center, double-blind, crossover study of 90 subjects, fluticasone propionate aqueous nasal spray, 200 micrograms, once daily was compared with 200 micrograms twice daily in severe seasonal allergic rhinitis to ragweed. The mean percentage of days free of nasal itching and eye symptoms was significantly higher with twice daily fluticasone propionate (P = .004, P = .005, respectively). There were no significant differences between the two treatment groups for nasal blockage, rhinorrhea (runny nose), and sneezing. The median symptom scores for nasal itching were lower during twice daily treatment (P = .008) but there was no significant difference for the other symptoms. There were no significant differences between the groups in the use of rescue medication. Adverse events were infrequent, and similar in both groups. Most were considered unrelated to the treatment. Twice daily treatment with fluticasone propionate may be preferable for some patients with severe seasonal allergic rhinitis.