Because most young children have difficulty in coordination for correct use of metered-dose inhalers (MDI), a trial of two spacer devices attached to MDIs was performed. In 13 children with asthma, aged 2-5 years old, a collapsible bag (Inspir-Ease) and a tube spacer (Aerochamber) were tested in a double-blind crossover trial with metaproterenol (1,300 micrograms). Respiratory resistance was measured by the forced oscillation method. Thirty minutes after metaproterenol administration there was a significant decrease in resistance with both spacers, while no significant change occurred after placebo administration. There was no difference in degree of bronchodilation between the two spacers. It is concluded that metaproterenol can be safely and effectively administered to preschool asthmatics by an MDI with spacer devices.