Axons often regrow to their targets and lost functions may be restored after an injury in the peripheral nervous system. In contrast, axonal regeneration is generally very limited after injuries in the central nervous system, and functional impairment is usually permanent. The regenerative capacity depends on intrinsic neuronal factors as well as the interaction of neurons with other cells. Glial cells may, in different situations, either support or inhibit axonal growth. This review discusses the molecular mechanisms that are involved in promoting and inhibiting axonal regeneration in the nervous system after injuries.