Tau pathology, associated with Alzheimer's disease, is characterized by the presence of phosphorylated and aggregated tau. Phosphorylation of tau takes place mainly in the vicinity of the tubulin-binding region of the molecule and its self aggregation is also mediated via this tubulin-binding region. Tau phosphorylation and aggregation have been related with conformational changes of the protein. These changes could be regulated by chaperones such as heat shock proteins, since one of these, heat shock protein 90 (Hsp90), has already been described as a putative tau-binding protein. In this work, we have confirmed the interaction of Hsp90 with tau protein and report that binding of Hsp90 to tau facilitates a conformational change that could result in its phosphorylation by glycogen synthase kinase 3 and its aggregation into filamentous structures.