Xenobiotics are chemical compounds foreign to a given biological system. In animals and humans, xenobiotics include drugs, drug metabolites, and environmental pollutants. In the environment, xenobiotics include synthetic pesticides, herbicides, and industrial pollutants. Many techniques are used in xenobiotics residue analysis; the method selected depends on the complexity of the sample, the nature of the matrix/analytes, and the analytical techniques available. This reference will help the analyst develop effective and validated analytical strategies for the analysis of hundreds of different xenobiotics on hundreds of different sample types, quickly, accurately and at acceptable cost.