The efficacy and safety of a new non-sedating antihistamine, loratadine (Clarityn, CAS 79794-75-5) 10 mg q.d., was compared to the classical antihistamine, hydroxyzine 25 mg t.i.d. and placebo in a 4-week (optional 12 week) randomized, double-blind, multi-center study in 203 patients with chronic idiopathic urticaria. Efficacy evaluations included weekly physician and patient assessments of pruritus, overall disease condition, and therapeutic response to treatment. Loratadine and hydroxyzine were significantly more effective than placebo and clinically comparable to each other as measured by all efficacy evaluations at each visit. Loratadine was safe and well tolerated with sedation and dry mouth similar to placebo and significantly less than hydroxyzine.