We investigated the effects of the antiasthmatic inhaled steroid budesonide at low and high dosage (0.6 and 2.4 mg/day) on calcium and phosphate metabolism (Ca, P) in 10 normal adults. Their endogenous production of cortisol dropped with budesonide treatment (p less than or equal to 0.0005), as did androgen production (p less than or equal to 0.003). This was associated with an increase in the renal tubular maximal reabsorption of Ca (p = 0.003) and P (p = 0.03), a decrease in the urinary output of Ca in the fasting morning state (p = 0.03), and an increase in serum P (p = 0.02). However, there was no change in the 24-h urinary excretion of Ca (p = 0.76) or P (p = 0.08) or the serum Ca level (p = 0.19). Similarly, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, parathyroid hormone, and urinary cAMP levels were not affected, indicating that absorption of Ca from the gut was not compromised. Thus, in contrast to the expected effects of oral steroid treatment, inhaled budesonide had no discernible short-term adverse effect on Ca or P metabolism under the conditions of this study, despite purposely using a dosage high enough to partially inhibit adrenocortical function. These data tend to support a broadening of the therapeutic role of budesonide, and possibly other inhaled steroid drugs, to include higher doses and more severe asthmatics. However, additional clinical and metabolic studies are needed to fully clarify the effects of high-dose inhaled steroid therapy on bone.