Spinal cord injury has devastating consequences because adult central nervous system (CNS) neurons do not regenerate their axons after injury. Two key reasons for axon regeneration failure are extrinsic inhibitory factors and a low intrinsic capacity for axon regrowth. Research has therefore focused on overcoming extrinsic growth inhibition, and enhancing intrinsic regeneration capacity. Both of these issues will need to be addressed to enable optimal repair of the injured spinal cord.