• Many children with asthma do not use the standard metered-dose inhaler (MDI) skillfully. To improve drug delivery, correct problems of hand-lung incoordination, and reduce local side effects, a number of spacer devices have been developed. We evaluated one such device, a tube spacer (Aerochamber), in 16 asthmatic children (5 to 12 years). On four separate days and in a randomized, double-blind, placebo-controlled manner, they received either metaproterenol sulfate by MDI aerosol (130 μg) or placebo with and without the tube spacer. To maximize techniques, at each visit the children had proper instructions, including viewing a videotape. Spirometry was performed at baseline and 5,15, and 30 minutes, and hourly for six hours, and the patient was monitored. Analysis of the entire group (forced expiratory volume at 1 s and midmaximal expiratory volume) revealed no difference between metaproterenol administered with or without the tube spacer, and both were significantly different than placebo through two hours. Six children had longer and three had better bronchodilatation with the MDI plus tube spacer than with the MDI alone. Side effects and vital signs did not differ between treatments. Under the circumstances of our study, the tube spacer device might enhance the use of the MDI in children who are not properly taught and/or who forget or cannot perform proper technique.