A method for determining surface charge decay [Q(t)], using a coaxial cylindrical capacitor arrangement and an electrometer interfaced to a PC, has been adapted so as to perform relatively straightforward measurement of resistivity in the surface region of insulators. A charge transport model is presented, based on Mott–Gurney diffusion, which allows interpretation of the data especially for the initial phase of surface charge decay. Resistivity measurements are presented for glass, mica, plexiglas, and polyethylene, covering the range 109–1018&OHgr; m, as an illustration of the useful range of the instrument for static and antistatic materials, particularly in film or sheet form. Values of surface charge diffusion constants have also been determined for the materials. ©1995 American Institute of Physics.