First published in 1999, Principles of Forensic Toxicology is now in its twentieth year of production. The book has remained a trusted textbook for students, and a reference book for laboratorians for two decades. Although the structure of the book remains unchanged, the fifth edition has been extensively revised to reflect new analytical methods, drugs, and special topics. A total of seven new chapters are included, bringing the total number of chapters to 40. In Part I—Introduction, a new chapter on drug-facilitated crimes was added. This complements the existing chapters on human performance and postmortem toxicology, in addition to performance-enhancing, pain management, and forensic drug testing. Significant updates were made with regard to Part II—Methodologies. Specimen preparation, chromatography and mass spectrometry chapters were extensively updated to reflect contemporary and emerging analytical approaches. New chapters on quantitative analytical methods, derivatization, statistics for forensic toxicology, and metrological traceability and measurement uncertainty were also added. These new additions further complement the existing method validation chapter and should provide a valuable resource to personnel in accredited forensic laboratories, and students preparing for the workplace.