The purpose of this study is to examine the effect of two different dose levels of estrogen or placebo in healthy postmenopausal women by measuring the changes in hormone levels and examining the changes in the uterine lining (endometrium).

Inclusion Criteria:

• Patient is a healthy postmenopausal woman less than or equal to 65 years of age with onset of menopause less than or equal to 10 years prior to prestudy visit 1
• Patient has a uterus and no history of uterine bleeding in the past 3 months
• Patient has not had a previous endometrial biopsy within the last 4 weeks
• Patient has had a normal mammogram within the last 11 months
• Patient has had a normal pap-smear within the past 3 years prior to screening
• Patient has had a normal transvaginal ultrasound of the endometrium
• Patient is willing to avoid strenuous physical activity such as strenuous or unaccustomed weight lifting, running, bicycling, etc for the duration of the study
• Patient agrees to not consume grapefruit products beginning approximately 2 weeks prior to the first dose of study drug and throughout the study
• Patient agrees to limit daily consumption of alcohol. During the study, daily alcohol consumption should not be more than 2 glasses
• Patient agrees to limit daily consumption of caffeine. During the study, daily caffeine consumption should not exceed 3 cups of coffee
• Patient is a non-smoker

Exclusion Criteria:

• Patient is mentally or legally incapacitated
• Patient has a history of any first degree relatives with breast or endometrial cancer
• Patient has a history of multiple and/or severe allergies to prescription or non-prescription drugs or food
• Patient has used any type of estrogen or progesterone preparation unless followed by appropriate wash-out periods
• Patient has had surgery, donated approximately 500 mL of blood or has participated in another investigational study within the last 4 weeks
• Patient has a history of deep vein thromboses, coronary artery disease, heart attack or stroke
• Patient is a current user of illegal drugs
• Patient has a history of hypersensitivity to estrogen products
• Patient is unable to refrain from using anti-coagulants

Reported AE data were collected during the period of the study from date of informed consent to the 14 day follow up period following completion of treatment.

Clinical staff telephoned subjects daily during the study, in between clinic visits and asked the subjects if they had experienced any adverse experiences.

The registered secondary outcome: "Mean gene expression intensity after 4 weeks of either 0.5 or 2 mg Estrace compared to placebo" results are not available because of inadequate quantity and quality of tissue samples that were obtained.