This is the first report on a series of researches in which an intensive study is to be made of factors related to overvoltage, so as to get a better insight into the mechanism of electrode potential and overvoltage. A list of questions concerning electrode potentials and overvoltage is given; also a list of possible stages in the process of ion discharge. Equipment is briefly described for obtaining the oscillograms shown of rapid changes in electrode potentials. Peculiar maxima in the IR and cathode curves are discussed; the oscillograms presented show the influence of previous charge, current densities, and time of charge on these maxima. Agitation of electrolyte affects charge and discharge potentials. The results obtained can be explained if it is assumed that the back potential is due to the liberation through discharge at the electrode, even at the lowest applied potentials, of a sufficient amount of active material to set up a back potential equal to the applied potential, and that a part, at least, of the continuous current is required to replace that portion of the active material continually lost by diffusion or otherwise.