The effect of inhaled beclomethasone dipropionate and budesonide on the adrenal function was studied in 30 children (aged 7 to 15 years) with mild bronchial asthma. The trial was designed as a prospective double-blind parallel study of the effect of stepwise increase of either beclomethasone dipropionate or budesonide from 200 micrograms through 400 micrograms, to 800 micrograms daily in three consecutive periods of 4 weeks. At the end of each period, the adrenal stress response was evaluated by measurements of serum cortisol and androstenedione during a short adrenocorticotropic hormone test. The unstimulated diurnal production of glucocorticosteroids was assessed by measurements of free cortisol in 24-hour urine samples. Free cortisol in urine was found a valid measure of the total diurnal excretion of cortisol metabolites, since it exhibited a good correlation to the fractional cortisol metabolites measured by gas chromatography. The adrenal response to adrenocorticotropic hormone stimulation was unaffected by treatment or dose. The unstimulated diurnal production of glucocorticosteroids demonstrated a highly significant dose-related suppression in response to the inhaled steroids. No significant difference was found between the two topical steroids (probability value 5.3%), and yet the suppression was apparent in the group of children treated with beclomethasone dipropionate but not in the group of children treated with budesonide. Further studies are desirable in order to ascertain whether budesonide offers an improved ratio between beneficial anti-inflammatory effect and unwanted systemic activity.