Densities, viscosities, and diffusion coefficients were measured for two aqueous surfactants, pentaethyleneglycol-1-hexyl ether (C6E5) and the sodium salt of 1-hexanesulfonic acid (C6SO3Na), through the critical micelle concentration range, and the results were briefly discussed, The micellization process was treated as an equilibrium, The diffusion data could be well fitted using a quite narrow range of association numbers, n, and equilibrium constants, K.