This paper reports ionic conductivity of yttria-stabilized zirconia (YSZ)-Al2O3 composite membranes. The tape cast specimens were subjected to binder burnout (500 degrees C) and sintering (1550 degrees C) processes to obtain 200-300 mu m thick membranes. The ionic conductivity and microstructure of the membranes were characterized and are discussed in this paper. The ionic conductivity of the composite specimens was enhanced and was correlated with the number of charge carrier and their mobility. The solubility of Al2O3 in YSZ was minimal and nanosize Al2O3 of the batch sintered into microsize and existed as a distinct phase. The scanning electron microscopy micrographs revealed that YSZ and Al2O3 grains were strained.