The inheritance of the epsilon4 allele of the apolipoprotein E (apoE) gene is the major genetic risk factor for developing late-onset Alzheimer disease. In transgenic mice overexpressing amyloid precursor protein (APP), replacing the endogenous mouse apoE gene with the human apolipoprotein E4 (apoE4) gene alters the distribution of amyloid-beta (Abeta) deposits from the brain parenchyma to the vasculature. However, the effects of this distribution on the onset and progression of tau pathology remain to be established. To address this issue, we used a genetic approach to replace the endogenous apoE gene with the human apoE4 allele in the 3xTg-AD mice. We showed that changing Abeta distribution from the parenchyma to the vasculature drastically reduces the tau pathology. The 3xTg-AD mice expressing the human apoE4 gene were virtually depleted of any somatodendritic tau deposits. These data strongly suggest that the somatodendritic tau accumulation is dependent on the parenchyma Abeta deposits.