Bilateral adrenalectomy is an acceptable alternative treatment in salt-wasting 21-hydroxylase deficiency when conventional steroid replacement therapy fails to control hyperandrogenism. Objections to surgical adrenalectomy have been based on surgical risk, possible loss of protective adrenal function, and the risk of ACTH-induced activation of adrenal rest tissue. We report a young female with salt-wasting CAH, who underwent bilateral adrenalectomy and developed severe hyperpigmentation, progressively marked corticotropin hypersecretion to concentrations seen in Nelson's syndrome (5,000-7,000 pg/ml), a pituitary microadenoma 5 years postoperatively, and probable ectopic adrenal rest tissue. Corticotropin concentrations failed to respond to ovine corticotropin-releasing hormone (oCRH) (1 microg/kg given as an i.v. bolus), but did suppress following both hydrocortisone administration (100 mg given as an i.v. bolus) and a low dose (0.5 mg given orally every 6 h for 48 h) dexamethasone suppression test. Patients with CAH have hyperactivity of the hypothalamic-pituitary-adrenal axis and are at risk for pituitary tumor formation.