The GSH-Glo™ Glutathione Assay is a luminescence-based assay for the detection and quantification of glutathione (GSH). The assay is based on the conversion of a luciferin derivative into luciferin in the presence of glutathione, catalyzed by glutathione S-transferase (GST). The signal generated in a coupled reaction with firefly luciferase is proportional to the amount of glutathione present in the sample. Luminescence is generated in less than one hour. The assay generates a stable luminescence signal and is simple, fast and easily adaptable to multiwell formats such as 96- and 384-well plates. This assay can be used for detection and quantification of GSH in cultured cells or in various biological samples.