Eighteen children aged 10.3 +/- 2.4 years who needed regular use of antiasthmatic drugs and showed after abandoning them with the appropriate intervals a FEV1 below 85% of their highest previous value, received in a randomized, double-blind crossover fashion two puffs of terbutaline 1 hour apart on two consecutive days. The drug was administered either with the conventional inhaler or a 10.3 X 2 cm. Forced spirometry, peak flow, flow-volume loops, and whole body plethysmography were performed basally, and 5, 15 and 45 minutes after each puff. The peak increase of the FEV1 was greater with the spacer (41.7% vs 30.4%, p less than 0.05). The increase of FEV1 was higher with the spacer at 5 minutes following the first puff and at 15 and 45 minutes after the second puff. No difference was observed in the other variables measured. Sixteen inhaled the drug "coordinatedly". The spacer offers some advantage in asthmatic children who inhale terbutaline mostly in a coordinated way.