In a double-blind, placebo-controlled study, the response of lung function to albuterol, topically administered by a metered-dose inhaler (MD) through a baby-adapted auxiliary device, was evaluated in 36 wheezy infants (1.6 to 25.2 months of age; median 8.1 months). The auxiliary device contains an air chamber of 350 ml and two low-resistant valves separating the inspiratory from the expiratory line. After baseline lung function measurements by infant whole-body plethysmography, the patients were randomly assigned to inhale either three times two puffs albuterol (100 micrograms/puff) or three times two puffs placebo at 5-min intervals. Changes in the degree of pulmonary hyperinflation, estimated by thoracic gas volume (TGV) and/or in the degree of bronchial obstruction, estimated by thoracic gas volume (TGV) and/or in the degree of bronchial obstruction, estimated by airway conductance (Gaw), were measured at 5-min intervals for up to 30 min. TGV and Gaw were expressed as standard deviation scores (SDS) of values predicted, and patients improving TGV and/or Gaw more than 2 SD were considered responders. In comparison with placebo, a significant percentage improvement in TGV (by the mean 26 to 53%) and a significant percentage improvement in Gaw (by the mean 34 to 51%) could be found in the active treatment groups. The study documents the usefulness of a new auxiliary device for the administration of aerosolized bronchodilators to wheezy infants.