Terfenadine was evaluated for the relief of symptoms in patients with allergic pollinosis on a double-blind basis. Terfenadine 20 mg 3 times daily was as effective as chlorpheniramine maleate 4 mg 3 times daily. Chlorpheniramine consistently showed a higher incidence of sedation than placebo. None of the terfenadine dosage schedules up to 200 mg 3 times daily caused sedation significantly different from that of placebo. Terfenadine appears to be the 1st antihistamine to lack significant CNS effects.