Post-menopausal hormone use is becoming increasingly widespread based on evidence of the benefits of estrogen use for bone and the heart. However, because estrogen alone substantially increases the risk of endometrial cancer, estrogen users who have not undergone a hysterectomy are frequently also placed on a progestogen (E/P), a strategy that reduces the likelihood of endometrial cancer when compared with use of estrogen alone. In 1991, there were almost no data on the risk of cardiovascular disease in post-menopausal women who used E/P combinations.