Abstract: β-Amyloid peptides (Aβ) are the main protein components of neuritic plaques and are important in the pathogenesis of Alzheimer's disease. It is reported that Aβ itself is not toxic; however, it becomes toxic to neuronal cells once it has aggregated into amyloid fibrils by peptide–peptide interactions. In this study, to specify the molecular mechanism of aggregation, a novel fluorescence assay was designed. For this purpose, possible partial peptides (38 types of 5-mer) were synthesized on solid-phase. The molecular interactions were examined by a fluorescence probe possessing Lys-Leu-Val-Phe-Phe (KLVFF) as a molecular recognition site. KLVFF is known to be a minimum sequence for formation of the Aβ aggregate. A specific interaction was observed between labeled and immobilized KLVFF. It suggests that the aggregation of Aβ was controlled by the recognition of KLVFF itself by hydrophobic and electrostatic interactions.