Nineteen outpatients with stable obstructive pulmonary disease (mean forced expiratory volume in one second [FEV1], 1.00 + 0.10 L) were evaluated for airway response to albuterol (salbutamol) administered by metered-dose inhaler and Bosch ultrasonic nebulizer (BUSN). Albuterol administered by metered-dose inhaler but not by nebulizer caused a significant increase in FEV1 and the mean forced expiratory flow over the middle half of the forced vital capacity (FEF25-75%) (p less than 0.02). Absolute increase from baseline of FEV1 and FEF25-75% was significantly greater for metered-dose inhaler (0.21 +/- 0.05 L; 0.32 +/- 0.13 L/sec) compared to ultrasonic nebulizer (0.07 +/- 0.03 L; 0.03 +/- 0.04 L/sec) (p less than 0.02). In 11 subjects (mean FEV1, 1.08 + 0.14 L), the placebo effect of inhalation of the diluent from the metered-dose inhaler (Freon) and the ultrasonic nebulizer (isotonic saline solution) was determined. Freon produced the mean increase of 1.5 percent, whereas the ultrasonic aerosol of isotonic saline solution resulted in a mean decrease of 8 percent in FEV1. Therefore, the inferior response to albuterol administered by ultrasonic nebulizer was at least in part due to the superimposed broncho-constriction occurring with ultrasonically administered saline solution. The metered-dose inhaler was more effective than the ultrasonic nebulizer for administration of albuterol in stable obstructive pulmonary disease, and the latter device is not recommended. A specific ultrasonic nebulizer should be prescribed only if its superiority to a metered-dose inhaler can be objectively documented.