Composite solid electrolytes in the system [(BaCl2)(1-x):(KCl)(x)](1-y):(ZrO2)(y) were prepared following the conventional ceramic powder processing route. In the mixed matrix system prepared by melt quench technique, a nominal increase in conductivity (sigma) was found in (BaCl2)(0.9): (KCl)(0.1). On ZrO2 particle dispersion in this mixed matrix, the maximum conductivity (similar to90 times that of base matrix value) was found to occur with 50 m/o of ZrO2. Conductivity increases monotonically over the temperature range from 100 to 300 degreesC studied and attains the value of 10 x 10(-6) S cm(-1) at 300 degreesC. The mobility (mu) of the charge carriers at room temperature was found to be 18.5 x 10(-2) cm(2) V-1 s(-1) and the increase in mu with temperature was not very significant. The transference ionic number determination showed that the electrical conductivity of the electrolyte is predominantly due to ions. This study indicates that the conductivity is governed by mobile ion concentration. (C) 2004 Elsevier Ltd. All rights reserved.