To assess the inhibitory effect of triamcinolone acetonide on pituitary-adrenal axis, we measured plasma cortisol, plasma ACTH and performed short ACTH stimulation test before and after injection of 40 mg of triamcinolone acetonide intramuscularly in 34 asthmatic patients. At the same time salivary cortisol levels had been followed up for four weeks in ten of the 34 patients. Maximum adrenal suppression was found in two to three days after the administration. The suppression rates of salivary cortisol, plasma cortisol, plasma ACTH and ACTH stimulation test were 81.5%, 53.2%, 70% and 45.6% respectively. Such suppression lasted for two weeks. Afterwards the secretion of pituitary and adrenal glands recovered gradually. The secretion of plasma ACTH and salivary cortisol returned to normal in four weeks and that of plasma cortisol in five weeks. Triamcinolone acetonide, 40 mg monthly, is comparable with prednisone 10 mg daily, or oral dexamethasone 0.75 mg daily. The inhibitory effect of the steroids on pituitary-adrenal axis was in the order of dexamethasone, triamcinolone acetonide and prednisone.