A model has been developed for fluidized bed electrodes based on an operative bipolar mechanism and the concept of two bipolar aggregates of particles in the direction of current flow, Extensive measurements of local overpotential frequency distribution and time-averaged overpotentials using a probe electrode technique have been made in both monopolar and bipolar packed bed electrodes, and in both monopolar and bipolar fluidized bed electrodes, Validation of the probe for overpotential measurement is claimed; and good agreement between fluidized bed electrode measurements and the model has been shown, This validation of a reasonable model for bipolarity in fluidized bed electrodes should permit application in design and scale-up of such electrodes.