Fluticasone propionate aqueous nasal spray (FPANS) is a topically active glucocorticoid which has been successfully used for the treatment of seasonal allergic rhinitis (SAR). Topical levocabastine is a highly selective H1 antagonist which has been proposed as an alternative treatment of SAR. The purpose of this study was to compare the clinical efficacy of two topical nasal treatments, FPANS and levocabastine, in the treatment of SAR. Additionally, the effect of treatments on nasal inflammation was examined during natural pollen exposure. A group of 288 adolescent and adult patients with at least a 2-year history of SAR to seasonal pollens participated in a multicenter, doubleblind, double-dummy, and placebo-controlled study. Patients were treated with either FPANS 200 microg, once daily (n = 97), or topical levocabastine, 200 microg, given twice daily (n = 96), or matched placebo (n = 95) for a period of 6 weeks, starting from the expected beginning of the pollen season. Clinically relevant pollens included Parietaria, olive, and grass. Assessment of efficacy was based on scores of daily nasal symptoms and on nasal cytology of nasal lavage. Nasal lavage was performed immediately before, during, and at the end of treatment in 39 patients. FPANS significantly increased the percentage of symptom-free days for nasal obstruction on waking and during the day, rhinorrhea, sneezing, and itching. FPANS provided a better control for night and day nasal obstruction (P<0.02 and P<0.01) and rhinorrhea (P<0.01) than levocabas tine. In addition, fewer patients treated with FPANS used rescue medication (P<0.025). The percentage of eosinophils in nasal lavage was reduced only during treatment with FPANS. The results of this study indicate that FPANS 200 microg, once daily, provides a better clinical effect than levocabastine 200 microg, twice daily, in patients with SAR. Unlike levocabastine, FPANS significantly attenuates nasal eosinophilia during pollen exposure, a feature which may explain its therapeutic efficacy.