Ionic conductivity of La4/3 - y Li3yTi2O6 (LLTO), where y value is 0.21, dispersed by various amount of strontium titanate (SrTiO3) was measured by complex impedance method, and powder X-ray diffraction (XRD) measurements and scanning electron microscope (SEM) observations were carried out. With increasing SrTiO3 concentration. the conductivity decreased. At 34 mol%, the Bragg peaks at 11, 26 and 35 degrees in LLTO disappeared in XRD patterns and small non-angulated crystals were shown in SEM. The behavior of ionic conductivity was discussed by using the effective medium approximation (EMA) theory. (C) 2008 Published by Elsevier B.V.