Voltages across various glabrous (and gland-free) regions of cavy skin range from 30 to 100 mV, inside positive; across hairy ones, 0 to 10 mV. (moreover, hairy areas also tend to maintain lower transcutaneous voltages in man.) When an incision is made through the glabrous epidermis of the cavy, a microampere flows through each millimeter of the cut's edge. These wound currents generate lateral, intraepidermal voltage gradients or fields of about 100-200 mV/mm near the cut; fields which decline with distance from the cut with a space constant of 0.3-0.4 mm. It is deduced from these data that the epidermis near a cut drives up to 300 microA/cm2 across itself; moreover, these currents and potentials can be grossly, rapidly, and (to some extent) reversibly reduced by amiloride. It is concluded that the hair and gland-free skin of cavies has a battery comparable in power and character to that of frogs; but it is suggested that this mammalian battery may primarily subserve epidermal wound healing rather than salt uptake.