An in vitro epiphyseal-plate model was subjected to various electrical fields. At a voltage gradient of 1500 volts per centimeter, a consistent, highly significant acceleration of growth of the epiphyseal plate occurred as measured from photomacrographs and as indicated by incorporation of 45Ca, 35S, and 3H-thymidine. The growth acceleration was due to voltage gradients and not to current flow. Although the mechanism of action of the electrical field is not known, it is obvious that the voltage gradient, either directly or indirectly, incites a physiological response of the growth-plate chondrocyte.