This work is devoted to studying of amyloid fibrils structure with benzothiazole thioflavin T (ThT) dye. Our data prove that ThT molecules incorporate in amyloid fibrils in monomeric form and there is no ground to suppose the formation of ThT dimers, eximers, or micells. Information concerning ThT — amyloid fibrils binding parameters and spectral properties of bound dye was obtained by absorption spectrophotometry of solutions prepared by equilibrium microdialysis.