The present paper summarizes our experience with the use of motor evoked potentials (MEP) and cerebellar evoked potentials (CEP) to assess the physiological integrity of the motor tracts of the spinal cord in a rat model. The MEP elicited by intracortical microstimulation of motor cortex reflected activity only in the pyramidal tracts; in contrast the MEP obtained by extradural cortical stimulation with a macroelectrode also reflected activity in a number of non-pyramidal pathways including the lateral vestibulospinal and rubrospinal tracts. The CEP was principally conducted in ventral spinal cord tracts and may reflect direct activation of brainstem nuclei. Data are presented which correlate the relationship between the MEP and axonal integrity after cord injury.