Moist bovine cortical bone specimens were milled to exact dimensions and subjected to bending stress under carefully controlled conditions. The surface under compression was consistently electronegative with respect to that under tension, and potentials up to 7.6 millivolts were recorded. With loads above one kilogram the relationship of peak voltage to load was nearly linear while the relationship of voltage to rate of load was non-linear, the increments in voltage being small beyond a certain rate. Under constant load there was a steady-state potential that was directly proportional to the load but not dependent on the rate of loading. A mathematical equation was derived relating voltage to time, load, and load rate. Although the potentials were clearly stress-induced, and perhaps more accurately strain-related, their origin could not be determined from these studies.