A double-blind study was performed to demonstrate that bronchodilator can be administered reliably to infants and children under 3 years of age from a metered-dose inhaler (MDI) by means of an economical valved aerosol-holding chamber device (Aerochamber) fitted with a mask. Symptoms of cough and breathlessness were compared for two 1-week crossover periods with the child either taking active drug or placebo. The MDI and Aerochamber with mask is an effective delivery system for respiratory therapy in these young children.