The low-frequency (100–10−4 Hz) behavior of metal-oxide varistors is obtained from analysis of the charging and discharging currents which flow upon the application and removal of a step voltage. These results are compared to data for the complex dielectric constant ε=ε′−iε″ obtained using an ac bridge in the frequency range 101–10−1 Hz. The presence of long-time polarization currents dominates the low-field low-temperature (T?0°C) dc response of these devices. When the varistor microstructure is taken into account the curves of ε″ (ω) versus frequency are consistent in slope and magnitude with other published data obtained on a wide variety of dielectric materials.