Although nonsecreting suprarenal embryonic remnants are frequently found in the urogenital tract, adenomatous transformation resulting in glucocorticoid excess is a rare phenomenon. We report a case of a 63-yr-old woman that presented with new-onset hirsutism, facial plethora, hypertension, centripetal obesity, and a proximal myopathy. The 24-h urinary free cortisol excretion rate was elevated, and the serum ACTH level was suppressed. The patient failed an overnight and low dose dexamethasone suppression test and did not respond to CRH stimulation. In light of the undetectable baseline morning ACTH levels and the blunt response to CRH, the diagnosis of corticotropin-independent Cushing’s syndrome was made. Imaging studies revealed normal adrenal glands and enlargement of a left pararenal nodule incidentally observed 4 yr before the onset of symptoms. Dramatic resolution of symptoms was observed after surgical removal of the 3.5-cm mass. Pathological exam confirmed adrenocortical adenoma in ectopic adrenal tissue. The case reported here represents the unusual circumstance in which the development of adenomatous transformation of ectopic adrenal tissue has been prospectively observed with imaging studies. It illustrates the importance of considering ectopic corticosteroid-secreting tumors in the context of corticotropin-independent Cushing’s syndrome.