The patient with Nelson's syndrome in this report represents an unusual case in which regular cyclic menstruation was preserved even though a large ACTH-producing pituitary adenoma was present. Despite normal menses and pregnancy, the radiologic findings of an enlarged sella turcica and an enhanced lesion on CAT scan were identified. This case demonstrates that patients with normal menstruation can have significant pituitary disease, and it exemplifies the need for regular follow-up examination to look for radiologic abnormalities in patients who have had adrenalectomy for treatment of Cushing's disease.