The experience gained with tamoxifen has been the basis for the new concept of selective estrogen receptor modulators (SERMs). The action of these substances has been investigated in both basic and clinical studies, but there is not an integrated view of all the facets of this recent area in modern medicine. This book offers an up-to-date compilation of the most relevant information on the topic carried out by experienced basic and clinical investigators. The first section revises the basic determinants required to understand the functional versatility of SERMs. This part includes chapters that review the main SERM families and their principal components, the mechanisms of action of steroid hormones, SERMs and pure antiestrogens, or and the action of SERMs on the hypothalamic-pituitary unit. The second part focuses on the clinical areas where SERMs have demonstrated efficacy, such as osteoporosis, breast cancer, cardiovascular disease, and benign gynecological pathology, including actions on the endometrium, etc. There is a final chapter offering a thoughtful reflection on the role that SERMs may have in clinical practice.