BACKGROUND: Intranasal corticosteroids are recommended as first-line therapy for allergic rhinitis (AR), and because of their pharmacologic class, hypothalamic-pituitary-adrenal (HPA) axis function is evaluated. OBJECTIVE: To evaluate whether cortisol production was suppressed (as a measure of HPA axis function) by 6 weeks of treatment with fluticasone furoate nasal spray, 110 microg once daily, in patients with perennial AR. METHODS: A double-blind, randomized, placebo- and active-controlled (prednisone), parallel-group study. Outpatients aged 12 to 65 years with perennial AR for 2 years or more were from 1 center in the United States and 1 center in Canada. Pharmacodynamic and pharmacokinetic samples were collected during 24-hour domiciled visits (overnight in clinic). Measurements included change from baseline in 24-hour serum cortisol weighted mean and 24-hour urinary free cortisol excretion, total 24-hour urinary free cortisol excretion and 6-beta hydroxycortisol excretion, and plasma concentration of fluticasone furoate. RESULTS: A total of 112 of 183 patients were randomized. Fluticasone furoate was noninferior to placebo with respect to the ratio from baseline in serum cortisol weighted mean (treatment ratio, 0.98; 95% confidence interval, 0.89 to 1.07). In contrast, use of prednisone, 10 mg once daily, significantly reduced the ratio from baseline compared with placebo. Change from baseline in 24-hour urinary cortisol excretion was similar in the fluticasone furoate and placebo groups. Plasma levels of fluticasone furoate were undetectable after 6 weeks of treatment. CONCLUSION: Fluticasone furoate nasal spray, 110 microg once daily, was not associated with HPA axis suppression in patients 12 years and older with perennial AR.