1 Acoustic rhinometry is a relatively new method for objectively assessing nasal airway patency. In this paper we compare acoustic rhinometry with active posterior rhinomanometry. 2 Twenty normal healthy volunteers underwent nasal challenge with either histamine or bradykinin, 100 mug to 1000 mug, and responses were assessed by acoustic rhinometry. A further 20 subjects received identical nasal challenges and responses were assessed by active posterior rhinomanometry. 3 On a subsequent occasion, the subjects challenged previously with histamine, were given the selective H-1-receptor antagonist, cetirizine, 10 mg orally, 3 h before repeat nasal challenge with histamine, 100-1000 mug. Again, responses were assessed by active posterior rhinomanometry and acoustic rhinometry. 4 The acoustic reflection measurements and the nasal airway resistance measurements showed comparable, significant dose-related changes in nasal patency to both histamine and bradykinin. Pretreatment with cetirizine blocked the histamine-induced change in nasal patency as measured by both methods. 5 We conclude that acoustic rhinometry has a number of advantages over posterior rhinomanometry. It is quick to perform, requires minimal subject co-operation and gives a reliable objective, measurement of dose-related changes in nasal airway patency before and after pharmacological treatment.