Objective: The aim of the study was to assess the efficacy and safety of RAD1901, an oral estrogen receptor ligand, for the treatment of moderate-to-severe vasomotor symptoms of menopause. Methods: This was a randomized, placebo-controlled, double-blind, dose-ranging, proof-of-concept trial. Postmenopausal women with a minimum of 7 moderate-to-severe, diary-reported hot flashes per day, or 50 per week, were randomized to one of five blinded dose groups (0 [placebo], 10, 25, 50, or 100 mg RAD1901 daily for 28 d). Efficacy endpoints included frequency and severity of hot flashes over 4 weeks of treatment. Results: One hundred participants were randomized across the five treatment regimens. The frequency of moderate-to-severe hot flashes decreased in all groups over the treatment period (mean percent change from baseline at 4 wk, -54.1%, -77.2%, -51.8%, -53.8%, and -67.0% for placebo, 10, 25, 50, and 100 mg groups). The response in the 10 mg group was significantly different from placebo at 4 weeks (P = 0.024). No other dose group was significantly different from placebo. There were no statistically significant differences in severity of hot flashes between placebo and any dose group. Treatment was well tolerated; most treatment-emergent adverse events were mild to moderate in severity. Conclusions: Daily treatment with 10 mg RAD1901 over 4 weeks resulted in a statistically significant reduction in the frequency of moderate-to-severe hot flashes compared with placebo, with an acceptable safety profile. Further clinical trials are warranted to investigate RAD1901's utility as a potential treatment for vasomotor symptoms.