The cmc and IC50 values of the β-amyloid (Aβ) aggregation inhibitors, 3-p-toluoyl-2-[4′-(3-diethylaminopropoxy)-phenyl]-benzofuran 1, and 2-[4′-(3-diethylaminopropoxy)-phenyl]-benzofuran 2 have been determined. After comparison of the cmc data and biological data (IC50 values), we conclude that these active benzofurans do not act as surfactants or micelles at the concentration required to inhibit β-amyloid-peptide aggregation.