Electroporation or electropermeabilization is a phenomenon observed when lipid bilayers, generally cell membranes, are exposed to high electric field pulses becoming transiently permeable to molecules that under regular conditions are not able to penetrate through them. This change in molecular permeability is believed to be produced by transient aqueous pores created in the lipidic structure and can be monitored by changes in the electrical conductivity of these membranes. The aim of this study is to use fast electrical impedance spectroscopy to measure the process of electroporation applied on cell monolayers growing attached to standard multiwell plates. The frequency response of the impedance can provide useful information about the extent of permeabilization in the cell membranes exposed to high electric fields and also the time dynamics of creation and resealing of these pores. For this study we used a microelectrode assembly specifically designed for in situ performance of both electroporation and impedance measurements. The design of the microelectrodes is based on a spiral geometry conceived to improve the uniformity of the electric field applied and to perform impedance measurements in a four-electrode configuration.