Ultrafiltration is a separation method at the nanometer scale and is applicable for the rejection of self-assembled surfactants at membrane surfaces. We investigated the filtration of reverse micelles in the ternary system AOT/isooctane/water. The dependence of flux velocity and rejection on pressure, size, and concentration of the reverse micelles is described. The changing composition of the ternary system during the filtration process was examined and is represented in a Gibbs phase triangle. The concentration of the reverse micelles at the membrane wall is discussed with a model established for aqueous polymer solutions.