Tau is a microtubule-associated protein with multiple splice forms 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. The Phospho(Thr231)/Total Tau Kit provides assay-specific components for the quantitative determination of phospho-tau (Thr231) and total tau in human and mouse brain homogenates and tissue culture supernatants.