This review focuses on the effects of electric fields on giant unilamellar vesicles, a cell-size membrane system. We describe various types of behavior of vesicles subjected to either alternating fields or strong direct current pulses, such as electrodeformation, -poration and -fusion. The vesicle response to alternating fields in various medium conditions is introduced and the underlying physical mechanisms are highlighted, supported by theoretical modeling. New aspects of the response of vesicles with charged or neutral membranes, in fluid or gel-phase, and embedded in different solutions, to strong direct current pulses are described including novel applications of vesicle electrofusion for nanoparticle synthesis.