While there are no doubts that APOE4 genotype and ApoE ε4 isoprotein are associated with the higher amount of fibrillar forms of Aβ deposits in the AD brain (Saunders et al., 1993; Schmechel et al., 1993; Kay et al., 2003; Ramanan et al., 2014), we have found that ApoE, in particular the ε4 isoprotein, at physiological concentrations is one of the strongest endogenous anti-Aβ fibrillization agents (Kumar et al., 2016). The gene discussed is APOE; the disease is Alzheimer disease.