The thermally stimulated polarization/depolarization current technique (abbreviated as TSPC/ TSDC) [1] is a useful tool for studying charge carrier motion in vitreous and crystalline solids. Recent works on alkali-containing oxide glasses [2-4] revealed the existence of three different polarizations named P1, P2, and P3 in the order of increasing peak temperatures within the temperature range of 80 to 700K. The P1 peak was assigned as being due to conduction polarization caused by conduction of alkali ions, the P2 pe~ to conduction polarization of the nonbridging oxygen ions in the alkali-depleted region near the anode, and the P3 peak to space charge polarization caused by the space charges built near the electrodes during conduction. The TSDC technique was originally developed for studying relaxation of the polarized impurityvacancy (l-V) dipoles in alkali halide crystal doped with divalent impurities [5]. The purpose of the present work was to gain further insight into the conduction polarization process in solid materials, with an emphasis on the difference in the polarization characteristics between glass and crystal. For a majority of glass compositions we observed a single dielectric loss peak at a frequency frn at which the relation