A 46 years old woman developed a sudden transcalvarial brain herniation 1 hour after removal of a huge right frontal arteriovenous malformation intraoperatively. In spite of all possible anes- thesiologic resuscitative treatments, the brain swelling was not subsided. Resuscitative resection of the frontal lobe was done. The brain CT taken immediately postoperatively showed a large unsuspected epidural hematoma over the contralateral left temporal and occipital areas. This rare complication should be remembered during brain surgery if unexpected brain swelling occurs without apparent reasons after resection of arteriovenous malformation.