Because some patients may prefer aqueous nasal sprays and once-daily dosing for relief of seasonal allergic rhinitis symptoms, a new aqueous formulation of triamcinolone acetonide (TAA Aqueous) was developed. We conducted a randomized, placebo-controlled, double-blind study to compare the efficacy and safety of once-daily administration of 220 micrograms/d of TAA Aqueous for 1 week, followed by either 220 micrograms/d or 110 micrograms/d for an additional 2 weeks, with that of placebo in 429 patients with seasonal allergic rhinitis. Patients recorded the severity of symptoms (nasal stuffiness, discharge, sneezing, nasal index [the sum of the first three variables], nasal itching, and eye symptoms) on daily diary cards. Patients' and physicians' global evaluations of efficacy were made at the end of the 3-week study period. Both regimens of TAA Aqueous significantly improved symptoms compared with placebo at most time points. Patients demonstrated significant improvements in nasal symptoms as early as the first day of treatment (within 12 to 16 hours based on treatment in the morning and symptom assessment at bedtime). Although TAA Aqueous 220 micrograms/d provided numerically greater reductions in nasal symptoms compared with 110 micrograms/d, these differences in efficacy over the last 2 weeks were not statistically significant. The incidence of adverse effects with both TAA Aqueous regimens was low and comparable to that of placebo. In summary, during the first week of therapy, TAA Aqueous 220 micrograms/d significantly reduced nasal symptoms. During the last 2 weeks of therapy, the 110 micrograms/d regimen of TAA Aqueous was effective as continued therapy for most patients. Both the 110 micrograms/d and 220 micrograms/d regimens of TAA Aqueous provided significantly better relief of nasal symptoms than did placebo.