The publication of this volume at this time appears particularly auspi cious. Biological, psychological, and social change is greater during the pubertal years than at any other period since infancy. While the past two decades have witnessed a virtual explosion of productive research on the first years of life, until recently research on adolescence, and particularly on puberty and early adolescence, has lagged substantially behind. This book provides encouraging evidence that things are changing for the better. Considered separately, the individual chapters in this book include important contributions to our growing knowledge of the biological mechanisms involved in pubertal onset and subsequent changes, as well as of the psychological and social aspects of these changes, both as con sequences and determinants. In this regard, the book clearly benefits from the breadth of disciplines represented by the contributors, includ ing developmental endocrinology, adolescent medicine, pediatrics, psy chology, and sociology, among others.