In 14 persons suffering from allergic, seasonal rhinitis the efficacy of 14-days treatment of cetirizine (Zyrtec 10 mg/day) was evaluated. The study was performed in double blind randomised method. Cetirizine was significantly more effective than placebo in reducing the clinical symptoms of rhinitis near in 60% patients. The improvement of nasal mucosa state in laryngological investigation was observed in patients who were better clinically. The inhalatory challenge test with histamine in 9 patients was positive and after cetirizine treatment the bronchial hyperreactivity disappeared.