A simple technique is presented for determining the zeta potential of large particles (>20 mu m) by streaming current measurements. The method has the advantage of not requiring correction for surface conductivity. The theory involves a description of pore space by either Darcy＇s law or the Kozeny-Carman equation. The simplifications introduced by assimilating the pore space to a bundle of capillary tubes are discussed. Results are presented for the variation of zeta potential with pH and ionic strength for a sieve cut of spherical glass beads and two different samples of irregular particles of silicon carbide.