Budesonide, a topically active corticosteroid, was administered in doses of 400 and 1,600 micrograms/day to 35 asthmatic adults, using a standard inhalation device or a tube or cone spacer. The spacers reduced oropharyngeal candidiasis by an amount equivalent to a 90% reduction in drug dose (p = less than 0.005) and doubled the drug's overall antiasthmatic potency (delta FEV1, p = 0.05) without significantly increasing its overall effect on blood eosinophils (p = 0.14) or the A.M. serum cortisol (p = 0.12). Steroid-induced neutrophilia increased by an amount approximating that produced by an extra half tablet of prednisone per day (p = 0.002). Both the airways and systemic effects of the spacers were greater in patients who had small airways dysfunction present prior to the study. The data suggest an increase in intrapulmonary drug deposition during spacer treatment without a material shift in regional delivery within the lung. Spacers should be particularly useful for patients whose response to inhaled steroid is compromised by by dose-limiting oropharyngeal complications. They can also reduce drug costs. They should be used selectively in children until their effect on regional intrapulmonary drug deposition has been more clearly defined.