ThepH and nature of anions were found to have a very significant effect on the rheological properties of zirconia suspensions. The variation in rheological properties withpH and anion type correlated well with the change in surface properties of zirconia. Zirconia suspensions with maximum yield stress and viscosity occurred at and near the isoelectric point (IEP). At apH where the magnitude of the electrophoretic mobility of the zirconia is high, a low viscosity dispersed suspension was obtained. The zirconia suspensions were dispersed with potassium hydroxide at highpH while hydrochloric acid or nitric acid was used for dispersion at lowpH. Sulfuric acid however did not disperse the suspensions at lowpH because of significant sulfate adsorption on the zirconia particle. Polycarboxylate additives (polyacrylate) shifted thepH of maximum yield stress of zirconia to a lowerpH. The degree ofpH shift increased with increasing concentration of polycarboxylate; an effect attributed to the adsorption of polycarboxylate on the zirconia particle and to the degree of adsorption which increased with increasing concentration of polycarboxylate.