A marked ionic change in both the intra- and the extracellular space at the site of an acute spinal cord lesion has been reported in the literature. The present study was undertaken to measure spontaneous electrical potentials that might be associated with the previously observed ionic shifts. With the use of an impact (weight drop) model of cord injury in rats, lesions were induced at T-8. DC potentials were measured simultaneously both rostrally and caudally with respect to site of injury over a time course of 4 hours after injury. The potentials were positive with respect to lesion site, and the intensity decreased with time during 4 hours of observation. These results seem to support reported ionic shifts and migrations in injured cords and represent, to our knowledge, the first reported measurement of spontaneous injury potential in the cord of a mammal.