A method for measuring the conductivity of ceramic powders has been developed using effective medium theory and impedance spectroscopy. Powders to be tested are mixed with aqueous solutions of varying NaCl concentrations to form a composite slurry. The impedance response of these powder-solution-composites (PSCs) is measured and analyzed using composite equivalent circuit and effective medium theories. Values obtained for a test powder of copper aluminate (CuAlO2) match closely to four-point dc values measured on bulk sintered bars. A comparison was also made in a system with highly composition-dependent conductivity (YITO, In2-2x2-yY2xSn2yO3, 0.08 less than or equal to x less than or equal to 0.20) to evaluate the upper and lower bounds for accurate measurements. Results from the PSC method matched the sintered bar four-point dc values within the range of NaCl solutions employed ( 0.5-10(-4) S/cm). (C) 2003 The Electrochemical Society.