GAP-43 is a growth cone protein expressed in neurons especially during periods of axonal elongation. Poor repair in the adult mammalian CNS has been ascribed to restraints upon its expression. We have cloned human GAP-43 cDNA to investigate its potential involvement in neurological illness. Analysis of postmortem human brain tissue disclosed uniformly high expression of GAP-43 throughout the neonatal brain, whereas in the adult brain high levels of GAP-43 persist only in discrete regions. However, in the wake of ischemic injury in the adult brain, regions normally low in GAP-43 reexpress it at high levels, suggesting a role for GAP-43 in remodeling and repair of mature CNS neurons.