The objective of this study was to assess the association of sex and the apolipoprotein E (APOE) ε4 allele with brain tau deposition and atrophy in older adults with Alzheimer's disease (AD) using quantitative 18F-AV-1451 positron emission tomography (PET) and magnetic resonance imaging (MRI). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.