In order to define metabolic brain changes associated with mild traumatic brain injury, proton magnetic resonance spectroscopy (MRS) was performed in patients with regional brain contusion and 13-15 of initial GCS score. The authors measured N-acetylaspartate(NAA)/creatine(Cr) ratio and lactate signal on in vivo proton MRS, which indicated cell loss and ischaemic dAmage respectively, in pericontusional oedematous areas (region of interest; ROI) adjacent to traumatic brain contusion on brain MRI to determine possible metabolic changes. The metabolic ratio of NAA/Cr and lactate/Cr peaks was measured both in the ROI and a corresponding region of the contralateral hemisphere (ROC) in seven patients and twenty-five normal control. In initial NAA/Cr ratios, the values of ROIs were significantly lower than those of the control (p = 0.009), but there was no difference either between ROI and ROC (p = 0.410) or between ROC of patients and the control (p = 0.199). In lactate/Cr ratios, the ROI in all seven patients and the ROC in two showed increased lactate signals. The lacate/Cr ratios of the ROIs were significantly elevated as compared to those of the ROCs (p = 0.02) and the control (p = 0.015). In 2-month follow up, lactate signals were absent or significantly reduced (p = 0.015). In no patients, clinical or radiological deterioration has been observed. Our results demonstrate that there is significant neuronal dysfunction in pericontusional oedematous areas as indicated by NAA/Cr ratios in the patients with mild head injury at both early and late stages. And there are significant ischaemic changes as indicated by increase of lactate level in ROI at early stage. These findings suggest that pericontusional oedematous areas can be vulnerable to secondary brain insults even in the patients with mild head injury.