Objective: To investigate the functional recovery following the transplantation of human embryonic stem (hES) cells into an injured rat spinal cord. Method: Sprague-Dawley rats were subjected to the spinal cord injury (SCI) using the New York University impactor. The rats were randomly allocated into three groups of 12 rats each, one media-treated and two hES cell-transplanted groups (5×10³/5Ռl, 2×10⁴/5Ռl). The hES cells were transplanted 1 week after a SCI. Results: The hES cells transplanted into the rats were found to promote the hind limb performance 8 weeks after transplantation. In the electrophysiological study, the transplanted rats showed significantly shortened latencies and increased amplitudes of motor and somatosensory evoked potentials, compared to the media-treated rats. In the spinal cord of the hES cell-treated group, the pathological findings including the glial scar formation and degenerative changes were attenuated and the human Tau protein-positive cells were identified in the vicinity of the necrotic cavity and in the white matter. Conclusion: These results suggest that the transplantation of hES cells might play a role in promoting the functional recovery after a SCI. (J Korean Acad Rehab Med 2008; 32: 491-500)