The purpose of this study is to determine whether RAD1901 is effective in decreasing hot flashes in postmenopausal women.

Inclusion Criteria:

1. Have documented evidence of a minimum of 7 moderate to severe hot flashes per day, or 50 per week.
2. Be in good general health as determined by medical history, physical examination, and inclusion procedures and is without evidence of any clinically significant abnormalities.
3. Have a normal pelvic assessment with no clinically significant signs on examination and pelvic ultrasound.
4. Have a normal mammogram at the time of study screening.

Exclusion Criteria:

1. A history of chronic or recurrent renal, hepatic, pulmonary, allergic, cardiovascular, gastrointestinal, endocrine, central nervous system, hematologic, immunologic or metabolic diseases to a degree that would compromise patient safety or interfere with the interpretation of study data. A history of active presence of thrombophlebitis, thrombosis, thromboembolic disorders.
2. A history of active presence of stroke, transient ischemic attack (TIA), heart attack or ischemic heart disease.
3. Unexplained vaginal bleeding within the 3 months prior to study entry.

Adverse events were collected for 2 months during this study; from start of treatment to the end-of-treatment visit (Day 29) and 30 days after end-of-treatment visit.

Method of routinely determining whether or not certain adverse events have occurred was by regular investigator assessment and regular laboratory testing.