Analytical toxicology is the detection, identi cation, and measurement of foreign compounds (xenobiotics) in biological and other specimens. Analytical methods are available for a very wide range of compounds: these may be chemicals, pesticides, pharmaceuticals, drugs of abuse and natural toxins. Analytical toxicology can assist in the diagnosis, management, prognosis, and prevention of poisoning. In addition analytical toxicology laboratories may be involved in a range of other activities such as the assessment of exposure following chemical incidents, therapeutic drug monitoring, forensic analyses, and monitoring for drugs of abuse. Analytical toxicology is important since it is the only means by which objective evidence of the nature and magnitude of exposure to a particular compound or group of compounds can be obtained. Most obviously such objective evidence is needed in a court of law, and most if not all countries have established analytical toxicology facilities as part of governmental forensic science laboratories. They may also be involved in research, for example in determining the pharmacokinetic and toxicokinetic properties of substances or the e cacy of new treatment regimens.