The electrokinetic properties of the process of cake filtration were investigated. Special interest was given to the streaming potential as a phenomenon and also as a measurement in the characterization of the dewatering properties of clay slurries. An apparatus capable of determining both the streaming potential and traditional dewatering properties such as specific resistance to filtration was developed and is described. Investigations regarding the influence of varying electrokinetic conditions on filterability and vice versa were conducted. The parameters deliberately varied were solid loading, filtration pressure, ionic species, and conductivity. The streaming potential observed during a single filtration run was constant. This is in accordance with the Helmholtz-Smoluchowski equation used in conjunction with D’Arcyan-based filtration theory, in which flow times superficial pore length is constant. The effects of conductivity, obtained by the use of various monovalent and divalent ions, showed that the specific resistance to filtration correlated with E/P, defined by specific pressure and conductivity. The significant effect of surface conductivity was demonstrated by varying the filtration pressure and by the tentative use of the corrections suggested by C. L. Rice and R. Whitehead [J. Phys. Chem. 69(11), 4017, 1965].