Despite its high frequency, there is not a consensus for the management of a patient with mild head trauma. In this prospective study we analyzed wether the transient loss of consciousness was associated with a higher risk of cranioencephalic injury in function of patient's age. Fifty-two patients with a Glasgow score of 15 at the Emergency Department but who reported a transient loss of consciousness were included. Patients were divided into two groups, patients aged > or = 60 years (n = 21) and patients aged < 60 years (n = 31). In all patients a head CT scan was performed. Nine abnormal CT scans were found in the group of patients aged > or = 60 years (three head fractures, three brain contusion, two subarachnoid haemorrhages, and one subdural haematoma) and one abnormal CT scan in the group of patients aged < 60 years (cranial fracture). This difference was statistically significant (p < 0.001). In conclusion, an urgent head CT scan should be performed in patients aged over 60 years with mild head trauma and loss of consciousness. In younger patients this scan should be performed when the patient presents with headache and vomiting.