In this study, using a large, neuropathologically defined cohort of postmortem brain samples with different APOE genotypes (N = 353), we biochemically investigated how APOE genotype is associated with the levels of major AD-related molecules, including Aβ40, Aβ42, total tau (tTau), phosphorylated tau 181 (pTau181), and apoE, in the presence of AGD and/or AD pathologies. The gene discussed is APOE; the disease is Alzheimer disease.