This introduction offers an overview of some of the contemporary issues associated with understanding the terms ‘sex’ and ‘gender’. In so doing, it provides the reader with an understanding of how these terms are used in this book. This chapter also explores the different ways in which it is possible to take account of sex and gender within criminology and victimology summarised as the ‘women and crime’ or ‘gender and crime’ debate. Again the reader is provided with an appreciation of the approach taken to this debate within this book. The introduction ends by offering an overview of the chapters that follow.