Using bioinformatics methods of investigation, amyloidogenic regions of Aβ16-25, Aβ31-40, and Aβ33-42, responsible for the formation of fibrils, were determined in the Aβ1-42 peptide. Fragments were synthesized in sufficient quantities, and the quality of the preparations was verified by mass spectrometric analysis. To study their amyloidogenic properties, methods of fluorescence spectroscopy (ThT binding), electron microscopy, and X-ray diffraction analysis were used. All three fragments under conditions of 5% DMSO and 50 mM Tris-HCl (pH 7.5) interact with ThT. At the same time fragments of Aβ31-40 and Aβ33-42 polymerize in the form of fibrils of different morphology, and fragment Aβ16-25 form polymers that are not typical of most amyloids in the form of films. According to X-ray diffraction data, the fibrils of all fragments show the presence of two main reflexes (4.6-4.8 Ǻ and 8-12 Ǻ), characteristic of the cross-β structure, indicating their amyloid structure. Analysis of the experimental data and structural modeling allowed us to conclude that the main building block in the formation of fibrils by fragments of Aβ1-42 peptide is a ring oligomer. The interaction of ring oligomers in different ways leads to the formation of polymers of different morphologies. Based on the data set, a new model of fibrillation was proposed.