In recent years, a number of textbooks on forensic science have been published, most of them directed to two groups, viz. the students of forensic science, and the customers so to say, (prosecutors, police officers, judges, defense lawyers). In this book, while covering fundamental concepts, we try to go a little further and address also active workers in the field of forensic chemistry. This is mainly achieved by relatively nu­ merous literature references. We hope that they may assist the forensic chemist in penetrating further into the subjects covered in this volume. At the end of most chapters there are examples of actual cases handled at the Swedish National Laboratory of Forensic Science. Many of these cases could, no doubt, have been investigated in greater detail, but they reflect the compromises often necessary for achieving a reasonable turnover. Some parts of the book are quite strongly colored by the personal opinions of the authors. We felt that these passages will give alittle more life to the text than in other treatises of a more objective, but possibly duller character. The authors welcome all constructive criticism which will help to improve the book, should there be a second edition.