Loratadine is a long-acting H1 antagonist devoid of anticholinergic and sedative effects. A double-blind, placebo-controlled, parallel-group study was performed in 69 patients to compare efficacy and safety of loratadine and mequitazine. Patients allergic to grass pollens were randomly assigned to one of the three treatment groups and followed up to 2 weeks during the peak of the pollen season. Symptoms of allergic rhinitis were evaluated at baseline and after 3, 7, and 14 days of treatment by the physician with patients rating their response daily on diary cards. Both loratadine and mequitazine induced a significant relief of nasal symptoms when these were compared to placebo. Loratadine was found to be significantly superior to placebo after 3 days of treatment, whereas a significant improvement was only observed after 7 days in patients treated with mequitazine. For nonnasal symptoms, none of the two anti-H1 antagonist induced a significant improvement, and this lack of effect may be related to low symptoms at baseline. Loratadine did not induce more side effects than placebo. Loratadine can be considered to be an effective and safe anti H1 histamine with a rapid onset of action.