SummaryThe bronchodilatory response of three β2-agonists (fenoterol, salbutamol, and terbutaline), administered by a metered aerosol inhaler, was assessed in 19 asthmatic children after histamine-induced bronchoconstriction. At 1-min intervals, the changes in total pulmonary flow resistance (R1) and dynamic lung compliance (C dyn) were measured. After rank-ordering according to the base line value of C dyn (62 to 200% predicted), the patients were divided into two groups according to lung compliance: (1) patients with greater compliance (C dyn, 129 to 200% predicted) and (2) patients with lesser compliance (C dyn, 69 to 116% predicted). The effect of the three bronchodilators on the mean decrease of R1and on the increase of C dyn was studied and analyzed for each drug separately. In all patients, salbutamol was the most efficient bronchodilator of small airways (P< 0.02). The most striking feature of this β2-mimetic was observed in patients whose lungs were initially overinflated (functional residual capacity over 120% predicted) but not obstructed before the histamine challenge (P< 0.005). In these subjects C dyn and R1are normalized after inhalation of salbutamol.After fenoterol and terbutaline inhalation, obstruction of the large airways was not fully alleviated. In addition, these two drugs seemed not to affect the ventilatory asynchronism (C dyn alterations) in patients whose lungs had been overinflated before drug inhalation (C dyn again around 150% predicted).