The effects of dioctadecyl dimethyl ammonium chloride (DODAC) on the theological properties of ternary systems consisting of behenyl trimethyl ammonium chloride (C(22)TAC), 1-hexadecanol (C16OH), and water are studied to improve the long-term stability and to establish the preparation method of cosmetic products. The basic ternary systems behave as solids at low stresses, due to the formation of lamella liquid crystals called alpha get. The additions of DODAC to ternary systems cause the rupture of alpha gel structures and transformation to vesicles. The structures of molecular assemblies are confirmed through particle size distribution, differential scanning calorimetry, and freeze fracture electron microscopy. The vesicle structures formed in coexistence of single-chain surfactant and double-chain surfactant are highly stable. Because the quaternary systems are considered to be constructed by the mixtures of alpha gel and vesicles at the appropriate concentrations of DODAC, the theology can be controlled by the structural balance between them. (c) 2006 Elsevier Inc. All rights reserved.