Tissue Specific Estrogen Action : Novel Mechanisms Novel Ligands Novel Therapies The multiple actions of estrogens on different cell types have not only intrigued endocrinology researchers but also inspired the development of selective estrogen receptor modulators or SERMs that modulate estrogen signaling in a cell type specific manner. Current molecular understanding of estrogen action has greatly profited from advances in molecular cell biology to dissect the mechanisms of estrogen regulated gene expression in target cells from in vivo analyses using genetic models deficient in estrogen signaling and from synthetic estrogen receptor ligands with isoform or pathway selective activity. These advances and their implications for clinical use were discussed by leading researchers from industry and academia during an international symposium held in Berlin 1 3 March 2006. Current molecular understanding of estrogen action has greatly profited from advances in molecular cell biology. These advances and their implications for clinical use were discussed by leading researchers from industry and academia during an international symposium held in Berlin 1 3 March 2006 and are featured in this volume.