BACKGROUND: Topical inhaled steroids, budesonide(Bu) and beclomethasone dipropionate (BDP), are now established as effective drugs in the management of chronic asthma. These drugs have high topical anti-inflammatory effect with low systemic activity. This study was performed to determine the effects of two inhaled corticosteroids, Bu and BDP, on the adrenocortical supression in 44 patients with bronchial asthma or chronic obstructive pulmonary disease. METHODS: The adrenocortical function was assessed by measurement of serum cortisol concentration at 8 o'clock in morning and free cortisol in 24-hour urine collection at interval in 44 patients. No steroid was administered during the pretreatment period of 10 days and the final 6 days of the study. Each subject inhaled BDP or Bu, in daily doses of 800 or 1,600 micrograms for 12 days. The dose was delivered by metered dose inhaler (MDI) or diskhaler or large spacing device attached to MDI. RESULTS: The levels of serum cortisol and 24-hour urinary free cortisol were decreased during the treatment period in patients inhaled Bu delivered by MDI in daily doses of 800 and 1,600 micrograms. In contrast, serum cortisol level was decreased on 6 and 12th day of treatment period in patients with BDP diskhaler in daily doses of 800 micrograms. In daily doses of 1,600 micrograms, the serum cortisol and 24hour urine free cortisol levels were decreased on 6, 9 and 12th day of treatment period in patients with BDP disk haler. The serum cortisol and 24-hour urinary free cortisol levels were not significantly decreased during the treatment period in patients inhaled Bu delivered by large spacing device attached to a MDI. CONCLUSION: These results showed that 1) the endogenous cortisol secretion was suppressed after inhalation of BDP and Bu in daily doses of 800 and l,600micrograms, 2) Bu with MDI suppressed the adrenocortical function more than BDP with diskhaler, in daily doses of 1600 micrograms, and 3)large spacing device attached to a MDI might decrease the risk of suppression in the hypothalamic -pituitary- adrenal axis.