We report the history, laboratory findings, and studies performed on a 27-yr-old patient with a metastatic parasellar adenoma of the pituitary and Cushing's syndrome. She developed intense hyperpigmentation and extraordinarily high ACTH levels after bilateral adrenalectomy in 1974. With the exception of marked hyperpigmentation, she did well on glucocorticoid replacement therapy until August 1979, when multiple hepatic nodules were observed during a cholecystectomy. Histological studies and immunoperoxidase staining indicated that these lesions were pituitary tumor metastases. What were presumed to be metastatic lesions also developed in lungs and bone. This combination of liver, bone, and lung metastases from primary pituitary tumors has not previously been reported. Immunoreactive plasma ACTH concentrations were as high as 230,000 pg/ml. Similarly, high levels of plasma immunoreactive beta MSH and immunoreactive beta-endorphin were found. High doses of glucocorticoids reduced the concentration of ACTH to one seventh to one tenth the basal level. The sensitivity of plasma ACTH to exogenous steroid administration strongly suggests that an intact intracellular mechanism for negative feedback control of ACTH secretion persisted within the tumor cells. The rapid rise in ACTH and related peptides and the development of metastases after adrenalectomy suggest that both the secretory capacity and the oncogenic potential of the parasellar tumor were chronically inhibited by glucocorticoid hormones.