Alzheimer̕s disease (AD) is a neurodegenerative disorder caused by the aggregation of the amyloid-beta peptide (Aβ), leading to amyloid plaques deposition in the brain. Although Aβ aggregation pathway still remains unclear, recent studies point out the enhanced toxicity of oligomers compared to fibrils. The E4 isoform of apolipoprotein E (ApoE) is the major risk factor in AD as people carrying one ɛ4 allele have significantly higher chances to develop the disease. Nevertheless, this phenomenon is still poorly understood.Our group has shown that attenuated total reflection Fourier-transform infrared spectroscopy (ATR–FTIR) could discriminate between Aβ42 oligomers and fibrils. Indeed, oligomers display anti-parallel β-sheet spectral components while fibrils are characterized by a parallel β-sheet organization. Using those spectral features to analyze the oligomeric content of our samples, we studied the influence of ApoE on Aβ42 aggregation. Our experiments demonstrated that ApoE3 increased the amount of Aβ42 oligomers in the sample.We can thus determine the proportion of Aβ oligomers in the presence of another compound in the sample. We plan to use ATR–FTIR to assess the effects of the other isoforms of ApoE on Aβ aggregation. Moreover, this could be extended to study the influence of other molecules or proteins on Aβ aggregation.