Objective This study aimed to better examine the relationship between hyperglycemia and outcome after traumatic diffuse axonal injury (TDAI). Methods We prospectively studied 118patients with moderate or severe TDAI [Glasgow Coma Scale scores (GCS), 3～12] who were treated conservatively in the surgical intensive care unit of zhuhai hospital between January 2000 and December 2004. Serum glucose, GCS and Glasgow Outcome Scale (GOS) of all the patients were measured: serum glucose, GCS score was recorded on admission, on days 3, 7 and 2 weeks; Outcome was determined by GOS score at discharge and after 3 months , respectively and the data were analyzed statistically to determine the relationship between serum glucose levels, severity of injury, and neurological outcome.Results Patients who died had significantly higher admission serum glucose values than those patients who survived (230 mg/dL vs 130 mg/dL, P＜0.005). Admission serum glucose ≥210 mg/dL was uniformly associated with a worse outcome. Conclusion Early hyperglycemia is a significant indicator of its severity, and a reliable predictor of outcome to TDAI.