In the posttraumatic period, measurement of neural tissue enzymes in serum and cerebrospinal fluid gives quantitative information about the severity of the head injury. In our study, we evaluated the relationship between the serum and cerebrospinal fluid levels of neuron specific enolase and the severity of trauma. Head traumas at different severity were applied experimentally (Mild 0.038 N, Moderate 0.057 N, Severe 0.3 N). Serum and cerebrospinal fluid levels of neuron specific enolase were measured in trauma and control groups of rats. Only in the severe trauma group, the neuron specific enolase levels of cerebrospinal fluid were significantly increased. There was no statistically significant difference between the groups when serum neuron specific enolase levels were evaluated.