Electrophoretic deposition (EPD) usually requires the use of non-aqueous colloidal suspensions, to avoid the problems of void formation by the electrolysis of H₂O. Recently, we found that no voids were formed in the deposit prepared by aqueous suspension using a palladium. The preparation and characteristics of suspensions are important for factors such as deposition rate, zeta potential, and particle size distribution. Experimental results showing the effect of washing on the stability and EPD for aqueous and non-aqueous suspensions of as-received zirconia (3 mol% Y₂O₃ doped tetragonal ZrO₂: Tosoh TZ3Y) and four kinds of alumina fine particles are presented here. The zeta potential and, hence, suspension stability, of TZ3Y-ethanol system were increased by washing. As a result, EPD rate increased dramatically from the as-received condition. There were no significant beneficial effects of washing on the aqueous system, indicating a much greater sensitivity to ionic contaminants in an ethanol suspension especially for the TZ3Y. Green densities prepared by EPD using aqueous suspensions were higher than those by EPD using ethanol suspensions and similar to those by slip casting using aqueous suspensions.