This paper compares cost-efficacy ratios for intranasal fluticasone propionate and terfenadine tablets within a sample of patients with seasonal allergic rhinitis symptoms due to mountain cedar allergy. Efficacy was assessed using secondary data analysis of patient ratings of symptoms and their overall assessment of response to treatment within a previously conducted clinical trial. Costs include direct costs of the drugs used for therapy. Patients with documented mountain cedar allergy who were 12 years of age or older (N = 232) had been randomized to either receive intranasal fluticasone propionate, terfenadine, or placebo. The cost-efficacy ratios for intranasal fluticasone propionate 200 micrograms once daily were more favorable than the ratios for terfenadine 60 mg twice daily. This relationship remained throughout the sensitivity analysis. Because intranasal fluticasone propionate is only available in a fixed package size, the number of efficacy-adjusted days of terfenadine therapy that could be purchased to reach break-even costs for a 30-day supply of fluticasone was calculated. Cost efficacy-adjusted days ranged from 11 to 18 days. If cost-efficacy adjustments are not conducted, the upper end of the range increases from 18 to 22 days, since 22 days of terfenadine could be purchased for the price of a 30-day supply of intranasal fluticasone propionate. Depending on which of the efficacy measures the reader believes, if patients use terfenadine for longer than 11 to 22 days, fluticasone propionate is the more cost-efficacious choice. Because most allergies are seasonal and allergy seasons typically last longer than 11 to 22 days, it is likely that fluticasone propionate will frequently be the more cost-efficacious choice in the patient population represented in this study.