This study will examine the safety and effectiveness of a synthetic hormone, CDB-2914, for treating symptoms of menopause. It will compare the effects of estrogen and CDB-2914 with those of estrogen and progesterone in postmenopausal women. The study will also evaluate whether CDB-2914 affects adrenal gland function. CDB-2914 is chemically similar to cortisol, a hormone that is produced by the adrenal glands and regulates the body's response to stresses, such as infection or injury.