Aminoglutethimide, a drug known to block adrenal steroidogenesis and peripheral aromatization of androgens to estrogens, has been found effective in the treatment of breast cancer. The drug has been used in our Institute to treat 71 consecutive metastatic breast cancer patients. Of 67 patients evaluable for response, 9 (13.4%) have achieved a partial response, 30 (44.7%) stable disease, and 28 (41.7%) progression of disease. Four patients were taken off the therapy because of drug-related toxicity.