Cations such as Ca2+ or La3+ show a strong tendency to bind themselves to the surface of anionic surfactant micelles. If the cation concentration is raised until micelles are saturated, the excess cations may precipitate with the surfactant monomer if the solubility product is reached. This paper describes the lauryl sulfate (DS)-Al3+ system. In this case, Al3+ reduces the g-potential to 0. The subsequent aggregation of micelles differs from micellar enlargement as known to take place generally in the transition from micellar solutions to liquid crystal. This aggregation is the mechanism of insolubilization of DS in the presence of Al3+, whereas in other cases precipitation of the monomer would be the mechanism. This effect deserves interest both because it provides additional information on the cation-micelle binding process and because the resulting aggregate has properties as an adsorbent of organic compounds.