During 3-year period, fourteen patients with air bubble in acute extradural hematomas were seen among 84 consecutively cases of extradural hematomas for a frequency of 16.7%. Extradural air were classified into 3 groups based on the location of air bubble ;frontal type(4 cases), temporal type(8 cases) & occipital type(2 cases). A skull fracture was seen in all cases & the air entrance was considered to frontobasal or laterobasal skull fractere. In patients with 4 cases of CSF leak & multiple air bubbles, delayed expansion of extradural hematoma was seen. The clinical significance of air bubble in acute extradural hematoma is disscussed.