Adrenalectomy was performed in 52 patients with metastatic mammary cancer. There were two postoperative deaths. Objective remissions of varying duration followed in 12 of 32 patients who had bilateral adrenalectomy alone and in 8 of 18 patients who also underwent oophorectomy. The extent of the lesions had little effect on the result, for two patients with metastases so extensive that one appeared moribund survived more than five years with great regression of the neoplasm. Experience led to four criteria for selecting patients most likely to be helped by adrenalectomy: age between 40 and 65 years, indications of slowness of neoplastic growth, a high titer of estrogenic substances in the urine, and a rather well-differentiated appearance of the tumor under the microscope. There was no evidence that simultaneous oophorectomy helped in women older than 54 years.