The authors report a study conducted in three Italian neurosurgical centres on 158 patients admitted after a minor head injury and with CT findings of a hitherto asymptomatic significant extradural haematoma. All patients were examined both prospectively by means of a computerized record containing 18 clinical and radiological parameters, and retrospectively by logistical regression analysis, in order to ascertain which factors influenced most the choice of surgical vs. conservative management. The size of the haematoma, rather than its location, and the degree of midline shift were the factors most influential in deciding in favour of surgical treatment, with a specificity of 0.83 and a sensitivity of 0.92. Conservative management of haematomas having a maximum thickness of less than 10 mm with a midline shift of less than 5 mm appears as safe. Outcome was "good recovery" in both the surgical and the nonsurgical patients, with only one death in the whole series, unrelated to the extradural lesion. This study focuses attention on a group of patients who are seldom examined by CT scan, but who can harbour potentially lethal lesions. Extension of CT scan examination to all adult patients with a minor head injury and a skull fracture can be recommended in order to identify significant haematomas in an asymptomatic phase.