The temperature variation of electroosmotic mobility corrected for the effects of Joule heating (mu(EOF)(0)) was employed to investigate the variation of the zeta-potential Q with temperature in fused-silica capillaries. Experimentally determined values for increased at 0.39% per degrees C, a rate that is about four to five times smaller than reported previously. Experimentally determined values of were directly proportional to the absolute temperature although values were also influenced slightly by changes to the dielectric constant. It was found that the effective charge density at the inner surface of the capillary was independent of temperature.