Glutathione (gamma-glutamylcysteinylglycine or GSH) is a naturally occuring tripeptide whose nucleophilic and reducing properties play a central role in metabolic pathways, as well as in the antioxidant system of most aerobic cells.1 GSH plays a critical role as a coenzyme with a variety of enzymes including, glutathione peroxidase, glutathione S-transferase and thiol transferase. GSH also plays major roles in drug metabolism, calcium metabolism, the gamma-glutamyl cycle, blood platelet and membrane functions. In addition, GSH is crucial to a variety of life processes, including the detoxification of xenobiotics, maintenance of the -SH level of proteins, thiol-disulfide exchange, removal of hydroperoxides and free radicals, and amino acid transport across membranes. Physiological values of intracellular GSH generally range from 1 to 10mM. Although many methods have been described for the assay of GSH, the reliable ones are labor intensive and not easy to use.