It is an exciting time for tau researchers as it is now generally accepted that abnormal tau species are required to mediate the toxic effects of amyloid β-peptide oligomers in Alzheimer's disease. Tau may play multiple roles in neurophysiology and there may be further pathologically relevant tau alterations, besides hyperphosphorylation and aggregation. The recent Biology and Pathology of Tau and its Role in Tauopathies II meeting explored these various aspects of tau, and presentations at the meeting, described in the following articles in this issue of Biochemical Society Transactions, are outlined in the present paper.