Selective estrogen receptor modulators (SERMs) have been the subject of extensive medicinal chemistry efforts at several pharmaceutical companies, including Merck. The Merck effort produced a wide variety of SERMs including ER-alpha selective antagonists and ER-beta agonists in addition to balanced (non-selective) analogs. This article will provide a broad overview of the Merck SERM medicinal chemistry effort as published in the literature through early 2008.