Apolipoprotein E (apoE) is an important part of the means by which lipids are transported in the nervous system. This transport system provides injured nerve cells, the cholesterol and phospholipids for the maintenance and repair of membranes, the growth of neurites, dendritic remodelling and synaptogenesis, and the effect of injury to the nervous system is now known in part to be modulated by the various isoforms of apoE. After the demonstration of an association between the apoE epsilon 4 and increased risk of subsequent development of both sporadic and late-onset form Alzheimer's disease, recent studies have provided additional evidence for the possibility that apoE may play an isoform-specific role in determining both the initial response and the subsequent consequences to acute brain injury. Further studies are required to better understand not only the response(s) of the nervous system to injury, but also the relationship between acute injury to the brain and the subsequent development of neurodegenerative disorders.