In this double-blind study forty-seven patients with hay fever were treated for 8 days with either terfenadine 60 mg twice a day, astemizole 10 mg once a day or placebo. On the second day of treatment terfenadine was statistically significantly superior to astemizole and placebo according to the ratings of symptomatology, efficacy and individual symptoms. The median onset of symptom alleviation was 3 hours for terfenadine and 2 days for astemizole. On the eighth day both astemizole and terfenadine were statistically significantly more efficacious than placebo, but no significant differences were found between the two drugs. Both drugs were well tolerated.