In this work, we studied the change of refractive index and the behaviour of electroconductivity with increasing temperature and concentration of the tetradecyltrimethly ammonium bromide (TTAB) + water binary lyotropic system. The phase diagram of this system has been drawn and the typical textures of the determined phases have been given. The correlation between phase states and physical properties such as refractive index and electroconductivity has been determined. The results on the phase states of the investigated system by using optical microscopy, electroconductivity measurements and refractive index measurements were consistent with each other. (c) 2007 Elsevier B.V. All rights reserved.