Exemestane is a new oral steroidal aromatase inactivator, active in postmenopausal women with hormonal sensitive breast carcinoma. This drug, at a dosage of 25 mg once daily, was shown to suppress in vivo aromatase activity by 97.9%, with a subsequent reduction superior to 85% of circulating oestrogen level. It exhibits definite antitumor activity at a relatively low daily dose, and is highly potent, highly selective, and well-tolerated. Moreover, for postmenopausal women with metastatic breast cancer, exemestane demonstrated a higher activity and lower toxicity profile when compared to megestrol acetate and tamoxifen in second- and first-line therapy, respectively. New data on exemestane are forthcoming both in the adjuvant and neoadjuvant setting, which could improve the management of early breast cancer in the future.