A grounding system is generally composed of several vertical, horizontal electrodes or grids. Excessive ground potential rises due to adjacent grounding electrodes can cause failures or misoperation of electronic devices and control systems. It is therefore necessary for computer-related and information-oriented equipment to be placed at a sufficient distance from the areas influenced by grounding electrodes. In this paper, in order to propose a method for evaluating the ground potential rise and interference in the vicinity of vertical grounding electrodes, the experimental and theoretical results on the potential interference between vertical grounding electrodes and its frequency dependence were described. The ground potential rise is sharply decreased with increasing the distance between grounding electrodes. In case that the separation of vertical grounding electrodes is less than 1.5[m], the potential interference coefficient was greater than 0.1 and linearly increased with the frequency of the test current within the frequency of 1[MHz].