Anion substituted lithium lanthanum titanate La2/3-xLi3x-yTiO3-yFy (x=0.11, 0 <= y <= 0.183) have been prepared successfully for the first time. Ionic conductivity of the compounds and its dependence on the content of fluorine ion and temperature has been systematically examined. Maximum lithium ion conductivity as high as 1.59 X 10(-3) S/cm at room temperature was obtained for La0.56Li0.258TiO2.928F0.072. The mechanism of the conductivity enhancement was analyzed on the basis of the substitution-induced change in bond-strength of the compound. (c) 2005 Elsevier B.V. All rights reserved.