The response to a beta2-agonist (salbutamol) was assessed by measuring specific airways conductance (sGaw) in healthy volunteers following increasing doses of inhaled or intravenous salbutamol. Regular inhaled salbutamol in doses exceeding 200 microgram four times a day produced a progressive loss of airways responsiveness to both inhaled and intravenous salbutamol (beta-agonist resistance). In salbutamol-resistant subjects full bronchodilator sensitivity was restored 3-5 h after intravenous hydrocortisone.