Tauprotein was a well‐studied molecule before it was discovered in the Alzheimer neurofibrillary tangles. As a microtubule‐associated protein (MAP), it continues to be of interest to microtubule biologists who have provided a rather rich knowledge about this protein. Recent work suggests thattau, a neuronal MAR is capable of generating some features of an axonal shape and an axon‐like organization of the cytoskeleton. The importance of tau in pathology stems from its relationship to Alzheimer paired helical filaments and dystrophic neurites.Tauwas first believed to be a component of paired helical filaments based upon immunocytochemical grounds (1–6) and then conclusively demonstrated by protein chemical techniques (7–9). Most recently it was shown that bacterially expressedtaufragments from the microtubule‐binding domain can self‐assemble into paired helical filaments that resemble those from the Alzheim