Cellular prion protein (PrPc) is a cell surface glycoprotein expressed in brain, spinal cord, and several peripheral tissues. Prion diseases, such as mad cow disease (bovine spongiform encephalopathy), scrapie, and Creutzfeldt-Jakob disease are fatal neurodegenerative diseases which result from conformational alteration of PrPc into a pathogenic form PrPsc (scrapie PrP). This enzyme immunometric assay (EIA) is based on a double-antibody sandwich technique and has been validated for the detection of native PrPc in brain extracts. It can also be used to detect PrPc extracted from other tissues, as well as denaturated PrP and recombinant PrP. The antibodies used in this kit were raised against scrapie associated fibrils (SAF) hamster brain and crossreact with PrP from most of mammalian species including mouse, human, sheep, and cattle. Each kit contains tracer, positive control, Ellman's reagent, EIA buffer, wash buffer, Tween 20, 96 well plate pre-coated with anti-prion protein mouse monoclonal antibody, well cover sheets, and complete instructions.