Tau is a microtubule-associated protein with multiple spliceoforms found primarily in neurons. Hyperphosphorylated tau is the major component of paired helical filaments and other large intracellular aggregates in the brains of patients with Alzheimer's disease and some other neurodegenerative disorders. This kit provides assay-specific components for the quantitative determination of both natural and recombinant human and mouse total tau in cerebrospinal fluid (CSF), brain homogenates, and tissue cultere supernatants.