Brain edema is a common pathophysiological process seen in many neurosurgical conditions. It can be localized in relation to focal lesions or generalized in diffuse types of brain injury. In addition to local adverse effects occurring at a cellular level, brain edema is associated with raised intracranial pressure (ICP), and both phenomena contribute to poor outcome in patients. One of the goals in treating patients with acute neurosurgical conditions in intensive care is to control brain edema and maintain ICP below target levels. The mainstay of treatment is medical therapy to reduce edema, but in certain patients--for example, those with diffuse severe traumatic brain injury (TBI) and malignant middle cerebral artery infarction--such treatment is not effective. In these patients, opening the skull (decompressive craniectomy) to reduce ICP is a potential option. In this review the authors discuss the role of decompressive craniectomy as a surgical option in patients with brain edema in the context of a variety of pathological entities. They also address the current evidence for the technique (predominantly observational series) and the ongoing randomized studies of decompressive craniectomy in TBI and ischemic stroke.