A novel, nondamaging method for experimental characterization of the formation and propagation of high-resistivity zones in CE, based on the measurement of time-dependent Joule heating on the outer capillary surface is proposed. The method detects propagation of resistive regions in capillaries in real time and allows the estimation of their velocity and resistance. The presented experimental data are in agreement with the results of the computer simulation as well as with previous data on the subject. The proposed method is useful for the development of new polymers as well as for the refinement and optimization of new CE protocols.