Sulforhodamine B (SRB) Cellular Cytotoxicity Assay is one of the most widely used methods for detecting the cell viability or cytotoxicity of drugs. This test is based on the ability of SRB to bind cellular protein components and to measure total biomass. SRB is a bright pink aminoxanthene dye that can form an electrostatic complex with basic amino acid residues of proteins under slightly acidic conditions, but can dissociate under basic conditions. It has been widely used for screening for drug toxicity against different types of cancer and non-cancer cell lines. In addition, this test is independent of cellular metabolic activity and therefore should show less interference by the test compounds. Since the binding of SRB is stoichiometric, the incorporated dye released from the stained cells after washing is directly proportional to the cell biomass and can be measured at 565 nm. This type of kit provides an excellent and effective method for in vitro cytotoxicity studies as well as high throughput drug screening.