A 35 year old female with Cushing's syndrome and bilateral adrenal macronodular hyperplasia, in whom a change from ACTH dependency to autonomy was observed, is presented. The diagnosis of Cushing's syndrome was based on the failure of suppression of urinary ketogenic steroids (17 KCS) and free cortisol (uF) with the administration of 2 mg of dexamethasone daily for 2 days. CT scan of the abdomen showed adrenal bilateral multinodular hyperplasia and the sellar CT scan was normal. Initially 8 mg for 2 days of dexamethasone suppressed 17 KCS and uF; however, a few months later this effect was lost as well as the effect of endogenous ACTH on cortisol. Bilateral adrenalectomy was carried out, prior to attainment of normal cortisol levels with Ketoconazole. The adrenal glands has multiple nodules and they weighed 10 and 21 grams. Her postoperative plasmatic cortisol levels were imperceptible. Physiopathologic mechanisms involved in bilateral macronodular adrenal hyperplasia are reviewed.