BACKGROUND The daily use of intranasal corticosteroids is approved for the treatment of seasonal allergic rhinitis. OBJECTIVE Our objective was to test the effectiveness of as-needed use of intranasal corticosteroids in the treatment of seasonal allergic rhinitis. METHODS A double-blind, placebo-controlled, randomized, parallel-group study of the as-needed usage of fluticasone propionate nasal spray in the management of seasonal allergic rhinitis was performed. Outcome measures were symptom score, Rhinitis Quality of Life Questionnaire (RQLQ), and the number of eosinophils and the level of eosinophilic cationic protein (ECP) in nasal lavage. RESULTS Twenty-six subjects in each group completed the 4-week study. The median symptom score over the duration of the study in the placebo group was 8.5 versus 4.5 in the active group. The active group had significant improvement on the interim visit in the sleep, non-nose/eye, activities, nasal, practical, and overall domains (P <.05) of the RQLQ and on the final visit in the nasal symptom domain. The number of eosinophils was significantly lower in the active than in the placebo group at the final visit. Changes in ECP were not significant. CONCLUSION As-needed fluticasone propionate nasal spray is efficacious in the treatment of seasonal allergic rhinitis.