bases provide easy access to this copious information, there was a clear necessity for a monograph-style textbook which assesses and summarizes current knowledge in this rapidly expanding field of research. It should be noted, however, that, due to this dynamic development, it is barely possible to comprehensively update every aspect of basic and clinical knowledge on estro­ gens and antiestrogens. Thus, the intention of the editors was to provide the reader with an overview of the "classic" and most recently explored areas of research and stimulate future interests in basic and applied endocrinology. Estrogens were among the first steroid hormones described in the scientific literature. Since they were first isolated, since the chemical, synthesic and pharmacological characterization of naturally occurring estrogens and, later on, of orally active derivatives, estrogen research has produced continu­ ously hallmark results in reproductive endocrinology worldwide.