In the last twenty years the efforts to design and optimize new drugs have been based on the three dimensional structure of the selected target proteins. In this regard, useful information has been achieved mainly by protein crystallography, which has recently turned from a low into a high-throughput process thanks to the improvement in robot technologies, automation procedure and the use of synchrotron radiation facilities [1-3]. This review examines the impact of Structure Based Drug Design (SBDD) on the discovery of ligands as the selective estrogen receptor modulators (SERMs) of the Estrogen Receptor (ER)α, which is involved in the regulation of several physiological and pathological processes.