Background: Allergic rhinitis (AR), an inflammatory disease of the nasal mucosa, affects approximately 25% of adults and 40% of children in the United States. Ciclesonide nasal spray is a corticosteroid being developed as a hypotonic formulation for AR. Objective: We sought to evaluate the efficacy, safety, and tolerability of ciclesonide nasal spray in adult and adolescent patients with seasonal AR (SAR). Methods: In this double-blind study patients (age, >= 12 years) were randomized to receive 200 mu g of intranasal ciclesonide (n = 164) or placebo (n = 163) once daily for 28 days. The primary measure was morning and evening patient-assessed reflective total nasal symptom score (TNSS). Additionally, instantaneous TNSSs, physician-assessed overall nasal signs and symptoms severity, and the results of the Rhinoconjunctivitis Quality of Life Questionnaire were evaluated. Adverse events were monitored throughout the study. Results: Ciclesonide significantly improved average morning and evening reflective and instantaneous TNSSs compared with placebo over days 1 to 14 (P < .001). Improvements were also noted over days 1 to 28 (P < .001) and over days 15 to 28 (P = .011). Ciclesonide was well tolerated. Conclusion: Intranasal ciclesonide was superior to placebo in relieving nasal symptoms in adult and adolescent patients with SAR. These results confirm the dose range-finding study in patients with SAR and support the efficacy of ciclesonide in AR. Clinical implications: In a clinical setting ciclesonide was shown to be safe and effective in the treatment of SAR in adolescent and adult patients.