A 45 year old female with Cushing's syndrome due to non-ACTH dependent bilateral adrenal macronodular hyperplasia (AMH) is reported. The diagnosis of Cushing's syndrome was based on the typical clinical features and on the demonstration of high urinary levels of free cortisol (microF) (630 micrograms/24 h) and 17 hydroxysteroids (17-OHS) which failed to suppress during the Liddle test (17-OHS, (mg/g creat), Basal: 68.5, post Dexamethasone 2 mg: 59.6 and post Dexamethasone 8 mg: 69.9). The adrenal CT scan showed bilateral multinodular enlargement while the pituitary CT scan was normal. Due to the presence of severe hypertension (240/150) and depression, the patient was treated with ketoconazole (800 mg/d) during 8 months achieving eucortisolism (microF 14-39 micrograms/24 h); however, plasma ACTH was not detectable at the end of this period. A bilateral adrenalectomy was performed, and both adrenals showed multiple nodules (0.3-4.5 cm in diameter) and weighed 136 and 31 g respectively. The lack of suppression of the 17-OHS with 8 mg of Dexamethasone, the persistence of an adequate inhibition of cortisol biosynthesis with ketoconazole, and the absence of plasma ACTH suggest that the patient had a non-ACTH dependent AMH. The possible pathogenic factors involved in this case are discussed.