When puberty is precocious is a question in and of itself. The possibility that puberty is st starting earlier in children of the 21 century has become a contentious topic during the past few years. It has received much attention in the medical literature as well as the lay press. As research methods and interpretation of data vary between the studies that have attempted to resolve this issue, we are pleased to present the reader with three very different approaches to addressing the same question. We are thrilled to have experts in the field of basic science share the most up-to-date understanding of the mechanisms involved in the complicated interplay of factors that initiate puberty in different species. Also reviewed in the book are the many fascinating causes of precocity and new observations regarding the influence of the in utero environment and the affect of adoption from a developing country on pubertal timing. We have also included cutting edge discussions of endocrine disruptors, and the often overlooked psychosocial ramifications of precocious puberty. We believe that this book will be useful to primary care providers as well as specialists who deal with issues regarding abnormalities of puberty and reproduction. The topics covered in these chapters will provide the reader with a solid understanding of the diverse and fascinating causes of precocious puberty and different treatment options.