Tau is a microtubule-associated protein th at can promote micortubulbe polymerization in vitro and can stabilize the asse mbled microtubules. Hyperphosphorylated form of tau comprises the main component of the paired helical filaments and neurofibrillary tangles found in Alzheimer s desease (AD). This paper reviews the functions and the prospects of tau in Al zheimers disease.