Despite the effectiveness of electrical currents in enhancing bone repair, there is little information in the literature on electrical parameters per se. Very little is known about the nature of the conduction mechanism or the current path between the electrodes. Without a better understanding it is difficult to establish meaningful hypotheses at the cellular level and to design relevant experimental protocols. In the present work, a first attempt is made at an in vivo delineation of the current-voltage relationship in the medullary area between two platinum electrodes embedded in the femur, by one of the techniques generally known to stimulate bone growth. At potential differences of less than 1 volt, a rather good ohmic dependence is observed, with an approximate specific resistance of 2 to 5 times 10-5 ohms/cm. At potentials higher than 1 volt, electrolytic processes appear to predominate and there is increasing non-linearity. Experimental techniques involving the adjustment of current through bone tissue assuming an ohmic dependence with little or no associated polarization effects are valid and certainly warrant further investigation.