The concept of selective estrogen receptor modulators (SERMs) has emerged recently in modern medicine. Two main features, the evidence of the wide expression of estrogen receptors in organs and systems and the growing information on the determinants of estrogen action, have allowed the envisioning of compounds with "a la carte" estrogenic profiles. The availability of substances performing as agonists wherever the estrogenic action is beneficial and as antagonists where it is not, is becoming less of a dream than of a closer reality. This book is an up-to-date review of the principal basic mechanisms and the clinical data integrating the actual current knowledge on SERMs.