This volume on conjugation enzymes and transporters serves to bring together current methods and concepts in an interesting, important and rapidly developing field of cell and systems biology. Phase II Conjugation Enzymes and Transport Systems focuses on the so-called Phase II enzymes of drug metabolism (xenobiotics), which has important ramifications for endogenous metabolism and nutrition. Also included are aspects on Phase III, transport systems. This volume of Methods in Enzymology presents current knowledge and methodology on glucuronidation, sulfation, acetylation, and transport systems in this field of research. Together with the volumes on Quinones and Quinone Enzymes (volumes 378 and 382), and on Glutathione Transferases and gamma-Glutamyl Transpeptidases (volume 401), the state of knowledge on proteomics and metabolomics of many pathways of (waste) product elimination, enzyme protein induction and gene regulation and feedback control is provided. This volume will help stimulate future investigations and speed the advance of knowledge in systems biology.