Low-frequency dielectric behavior of membrane/electrolyte systems was studied with artificial membranes made from thin plastic films and NaCl electrolyte of various concentrations. A low-frequency dielectric dispersion or relaxation, which is associated with membrane pores and membrane permeability, was observed and investigated. A qualitative explanation is proposed. Membrane structure characteristics, such as thickness, pore size, and number, were found to affect significantly the low-frequency dielectric dispersion, which indicates some potential applications for low-frequency dielectric measurements in membrane-or tissue-related areas.