Secondary degeneration affects uninjured neural tissue surrounding an initial insult and is associated with reactive oxygen species over production and oxidative damage. This thesis characterised the vulnerability of cellular subtypes within regions of secondary degeneration in vivo and found oligodendroglial progenitors the most susceptible to oxidative damage within the first week of injury. The acute oxidative damage to oligodendroglia! progenitors was associated with reduced expression of myelination-associated genes at later time points. Assessment of morphology within damaged regions showed compromised myelin structure along the lengths of axons in chronic neurotrauma lesions, likely contributing to t he lack of functional recovery after injury.