BACKGROUND: Aerosol-based corticosteroid nasal formulations may be preferred over current aqueous nasal sprays by some patients because they traditionally cause less pharyngeal and anterior nose runoff. OBJECTIVE: To determine the optimal dose, safety, and tolerability of ciclesonide hydrofluoroalkane nasal aerosol in patients with seasonal allergic rhinitis (SAR). METHODS: Patients 12 years or older with a history of SAR received ciclesonide hydrofluoroalkane nasal aerosol to a total dose of 75, 150, or 300 microg or placebo once daily (half dose per nostril) for 2 weeks. The primary efficacy assessment was patient-reported average morning and evening reflective (24-hour) total nasal symptom scores (rTNSS). Secondary efficacy assessments included patient-reported average morning and evening instantaneous TNSS (iTNSS), patient-reported morning iTNSS, physician-assessed nasal signs and symptom severity, and Rhinoconjunctivitis Quality of Life Questionnaire responses. Safety and tolerability were also assessed. RESULTS: Ciclesonide hydrofluoroalkane nasal aerosol demonstrated a statistically significantly greater reduction from baseline in average morning and evening rTNSS (24-hour) vs placebo, with treatment differences as follows: 0.81 (P = .001; 300 microg), 0.90 (P < .001; 150 microg), and 0.66 (P = .01; 75 microg). Improvements in average morning and evening iTNSS and patient-reported morning iTNSS were also significantly improved regardless of dose (P < or = .003 for all ciclesonide groups vs placebo). The incidence of treatment-related adverse events was low (< 1.6% for all) and similar among groups. CONCLUSIONS: Ciclesonide hydrofluoroalkane nasal aerosol demonstrated statistically significant improvements in SAR symptoms vs placebo. On the basis of comparable efficacy and safety profiles observed for all doses, these results suggest that the 75-microg and 150-microg doses of ciclesonide hydrofluoroalkane appear appropriate for further evaluation of efficacy.