Damage to the central and peripheral nervous system often produces lasting functional deficits. A major focus of neuroscience research has been to enhance functional restitution of the damaged nervous system and thereby produce recovery of behavioral or physiological processes. Promising procedures include surgical, physical, and chemical manipulations to reduce scar formation and minimize the disruption of support elements, administration of growth-stimulating substances, tissue grafts to bridge gaps in fiber pathways, and embryonic brain tissue grafts to provide new cells with the potential to generate fiber systems. Two elements are required for functional nervous system repair: (i) neurons with the capacity to extend processes must be present, and (ii) the regenerating neurites must find a continuous, unbroken pathway to appropriate targets through a supportive milieu.