The effect of two beta 2-adrenoceptor agonists, salbutamol (100 micrograms/kg i.v.) and broxaterol (100 micrograms/kg i.v.), on airway microvascular leakage induced by vagal stimulation was studied in anaesthetised guinea pigs. Airway microvascular leakage was measured by Evans blue extravasation. Broxaterol, but not salbutamol, inhibited Evans blue dye extravasation at all airway levels, an effect prevented by pretreatment with propranolol (1 mg/kg). Neither of the beta 2-agonists had any effect on substance P-induced Evans blue dye extravasation. Broxaterol inhibits the prejunctional release of tachykinins from airway sensory nerves by stimulation of beta-receptors. The mechanism by which beta-adrenoceptor agonists prevent airway microvascular leakage deserves further study.