Forty-five patients with residual or recurrent nasal polyposis after ethmoidectomy were treated with either cetirizine at twice the daily recommended (20 mg) dose or placebo for three months. The number and size of polyps remained unchanged during the study period. Cetirizine was found to reduce nasal sneezing and rhinorrhoea effectively. The drug also had a beneficial effect on nasal obstruction in the latter part of the study. The side effects of 20 mg (double the recommended daily adult dose) of cetirizine were few and comparable to placebo.