The field of endocrine disruption or endocrine active compounds (EACs), which is just emerging and still controversial, is comprehensively covered by leading experts in Volume 3, Subvolumes L (the present volume, Part I) and M (Part II). The major classes of endocrine active chemicals are discussed, as well as methods for their detection and their association with health disturbances in humans and wildlife. The etiology of several of the human diseases associated with endocrine disruptors, e.g. breast and prostate cancer, decreased fertility and malformations, is still poorly understood, and the current state of knowledge is presented. Since hormonally active agents appear to have the potential of both adverse and beneficial effects, the evidence of health benefits associated with endocrine active compounds in humans is also presented. Basic chapters on the mode of action of EACs and on the etiology of the associated diseases facilitate the understanding of this complex subject for non-medical readers.