Three cases of epidural hematoma are reported. They developed following craniotomy for supratentorial lesions on the contralateral side. Case 1 was a 27-year-old male. A left parietal epidural hematoma was observed after removal of a right acute subdural hematoma caused by head trauma. The epidural hematoma seemed to be induced by decompression of the injured middle meningeal artery which had been suppressed by intracranial hypertension. Case 2 was a 20-year-old female. A right frontal epidural hematoma developed following left frontal brain tumor removal. Case 3 was a 58-year-old female. She had a right parietal epidural hematoma after neck clipping of a left internal carotid-posterior communicating aneurysm. The mechanisms causing the epidural hematomas in Cases 2 and 3 were not clear. There is some possibility that development of the epidural hematoma was related to loose adhesion between the dura mater and cranium, and to the craniotomy performed by airdrill and airtome.