An electroporation device having a signal generating circuit (3) connectable at the output to electrodes (5) fittable to a substrate (35) having cells. The electrodes (5) produce an electric field which induces permeabilization of the cell membranes to facilitate introduction of substances into the cells. The amplitude of the signal (12) applied to the electrodes is closed-loop controlled on the basis of the impedance (Z(.omega.)) of the substrate, so as to regulate the amplitude of the signal following a reduction in impedance caused by permeabilization of the cell membranes.