This book is intended to provide detailed LC-MS/MS procedures for the analysis of several compounds of clinical signi fi cance.The fi rst two chapters provide the reader with an overview of mass spectroscopy, its place in clinical practice, its application of MS to TDM and toxicology, and the merits of LC-MS(/MS) and new sample preparation techniques.The remaining chapters discuss different approaches to screening for drugs of abuse and for general unknowns, as well as targeted measurement of speci fi c analytes or classes of analytes including abused drugs, toxic compounds, and therapeutic agents.We thank our colleagues who contributed to the content of the book for the many hours of work that these chapters represent.We hope that you, the reader, fi nd this book useful.