A total of 317 patients received loratadine, 10 mg once daily, terfenadine 60 mg twice daily, or placebo in a 14-day, double-blind, randomized study in seasonal allergic rhinitis. Four nasal and four nonnasal symptoms were evaluated. At the end point evaluation, mean total scores of combined nasal and nonnasal symptoms decreased from baseline (improved) 46%, 44%, and 35%, respectively, for loratadine, terfenadine, and placebo. The difference between loratadine and placebo treatment was significant (p = 0.03). Loratadine was particularly effective compared with placebo in relieving nasal discharge, sneezing, and itching/burning eyes. Therapeutic response to treatment was good or excellent in 66 (64%) of 103 loratadine-treated patients, 58 (56%) of 104 terfenadine-treated patients, and 48 (47%) of 102 placebo-treated patients. Adverse experiences reported during the study were usually mild or moderate and were not significantly different among the three treatment groups. Sedation (somnolence) was reported by 10 loratadine-treated patients, seven terfenadine-treated patients, and eight placebo-treated patients. Loratadine, 10 mg once daily, was comparable to terfenadine, 60 mg twice daily, and significantly superior to placebo in the symptomatic relief of seasonal allergic rhinitis.