The effect of partial and complete spinal cord injury (Th7-Th8) on locomotor activity evoked by epidural electrical stimulation (L5 segment, stimulation frequency 5 Hz, current strength 80-100 microA) in decerebrate cats has been investigated. It was established that the cutting of dorsal columns did not influence substantially the locomotion. The destruction of the ventral spinal quadrant resulted in the deterioration and instability of the locomotor rhythm. The injury of lateral or medial descending motor systems led to a redistribution of the tone in antagonist muscles. It was found that locomotion can be evoked by epidural stimulation within 20 h after the complete transaction of the spinal cord. The restoration of polysynaptic components in EMG responses correlated with the restoration of the stepping function. The data obtained confirm that the initiation of locomotion under epidural stimulation is caused by direct action on intraspinal systems responsible for locomotion regulation. In the case of intact or partially injured spinal cord, this effect is under the influence of supraspinal motor systems correcting and stabilizing the evoked locomotor pattern.