This chapter discusses the mechanisms of spinal cord plasticity in animal models as revealed by the recovery of motor functions after a spinal lesion. It shows that in cats, rats and mice, motor programs such as locomotion are re-expressed after a complete spinal transection at the low-thoracic level. The pharmacological work with intrathecal cannula suggested that important effects on locomotion could be observed when the intrathecal injections were localized to the rostral spinal segments. Clinically, the notion that certain spinal segments may play a critical role in the control of spinal locomotion may help to somewhat simplify where to target pharmacological stimulation, cell grafts or electrical stimulation. With the advent of genetic characterization and the potential for genetic manipulations, the mouse is becoming an increasingly important model for spinal cord injury research. The characteristics of motor patterns result from an intricate dynamic sensori-motor interaction between the spinal and supraspinal levels.