In this effort we used electrical impedance spectroscopy and a four-probe apparatus, the Electrical Properties Cup (EPC), to measure the properties of various lunar and martian soil simulants. The impedance values are characterized by a resistance-capacitor network that is used to determine the soil conductivity and dielectric constant. In this effort we measured the impedance of different types of martian soil simulants (Silica sand, Atacama Desert sand, and Moses Lake basalt) and lunar simulants. The results show that the soil impedance measurements are strongly dependent on water content and soil type and to a lesser extent particle size and electrolyte concentration. This presentation describes the experimental four-probe apparatus, procedures used to prepare the samples including soil washing and loading, and soil impedance measurements.