The function of the pituitary-adrenal axis was investigated in ten asthmatic children (5-14 years of age) before and after administration of beclomethasone-dipropionate as inhalation therapy in a dose of 300-600 micrograms/24 hrs, during six months. Cortisol diurnal rhythm, excretion of free cortisol in 24 hours urine and stimulation of plasma-cortisol after ACTH-administration were determined. The same investigations were carried out in a comparable group of ten asthmatic children already using this inhalation therapy for more than one year. Significant differences were found comparing 08.00 h. cortisol values of the children from the first group and those who used medication for more than one year. In this first group, the ability of the adrenal glands to be stimulated by ACTH-administration after six months of medication, decreased significantly as well. These results indicate an impairment of the function of pituitary-adrenal axis during long-term treatment with inhaled beclomethasone-dipropionate. This implicates a decreased ability of the adrenal glands to react in an optimum way in stress-situations. In these patients oral or parenteral administrations of steroids should be considered earlier in stress situations like a severe asthma attack.