Cerebral accumulation of hyperphosphorylated tau (phospho-tau) occurs in several neurodegenerative conditions including Alzheimer disease. In prion diseases, phospho-tau deposition has been described in a rare genetic form, Gerstmann-Sträussler-Scheinker disease, but is not considered part of the neuropathological picture of Creutzfeldt-Jakob disease. Aim of this study was to investigate whether changes related to phospho-tau accumulation are present in the brain of patients with variant Creutzfeldt-Jakob disease (vCJD) that shares with Gerstmann-Sträussler-Scheinker disease abundant prion protein (PrP) deposition in amyloid form. The analysis was extended to experimental mouse models of vCJD. We detected a large number of phospho-tau-immunoreactive neuritic profiles, often clustered around PrP amyloid deposits, not only in the cerebral cortex, but also in the cerebellum of all vCJD patients examined, in the absence of Abeta. Although less constantly, phospho-tau was localized in some perikaria and dendrites. The biochemical counterpart was the presence of phospho-tau in the detergent-insoluble fraction of cerebral cortex. Phospho-tau-immunoreactive neuronal profiles were also found in association with PrP deposits in mouse models of vCJD. These findings suggest that the abnormal forms of PrP associated with vCJD trigger a tauopathy, and provide a paradigm for the early stages of tau pathology associated with cerebral amyloidoses, including Alzheimer disease.