 A total of 643 actual504, initially proposed postmenopausal women were randomized according to their number of years since menopause, less than 6 years or 10 years or more, to receive either oral 17B-estradiol 1 mg daily or a placebo. Women with a uterus will also use vaginal progesterone gel 4 or a placebo gel the last ten days of each month. The vaginal progesterone will be distributed in a double-blind fashion along with the randomized treatment so that only women exposed to active treatment will receive active progesterone. As initially proposed, participants will undergo ultrasonography at baseline and every 6 months throughout the 2 to 5 years average 3 years of randomized treatment. Participants will also undergo cognitive testing at baseline and after 3 years of randomized treatment. The trial has been extended for an additional 2 to 2.5 years of randomized treatment overall average randomized treatment of 5 years and range of 2 to 8.5 years. Ultrasonography will continue to be collected every 6 months and upon completion of randomized treatment, participants will undergo cardiac CT for coronary artery calcium and coronary artery lesion measurements. Participants will also undergo a third cognitive testing at the completion of randomized treatment. 