Background and Purpose: Large hemispheric infarction affecting the whole middle cerebral artery territory implies a risk for massive edema formation and transtentorial herniation (malignant MCA-infarction). These patients have a mortality of 80 % with concervative medical treatment. Decompressive hemicraniectomy has been proposed as a life-saving treatment for malignant MCA-infarctions, but its efficiacy in reducing mortality and disability is still uncertain.The purpose is to review the litterature to se if the effect of decompressive hemicraniectomy has been proven from the aviable data, and to identify factors affecting the functional outcome.Methods: Search in Pubmed and Embase resulted in 36 studies published after 1990 reporting ¡Ý 5 patients. These were evaluated for mortality and disability. Studies which reported individual data were in addition evaluated for age, side of infarction, vascular territory of infarction, and time to surgery. There were no published randomized controlled trials.Results: 36 studies reported a total of 1109 patients. 806 survived, which gives a mortality of 27,3%. 29 studies reported on the functional outcome of their patients: 260 of 637 (40,8%) surviving patients has an acceptable functional outcome (BI ¡Ý 60, mRS ¡Ü 3, GOS 4-5). 8 studies compared patients treated with decompressive hemicraniectomy to patients treated conservatively. The surgically treated patients had a total mortality of 25%, while the conservative treated group had a total mortality of 61%. However these studies do not meet the criteria for controlled trials.16 studies reports individual data: Of 183 patients aged > 50 years, 36,6% were dead, and 65,5% of the surviving patients were severely disabeled (BI < 60, mRS 4-5, GOS 2-3). Compared with the 115 patients ¡Ü 50 years there 11,3 % were dead, and 37,3% of the surviving patients were severely disabeled.Involvement of more than one vascular territoy, side of infarction, and time to surgery seemed to have little impact on mortality and disability.Conclusion: Decompressive hemicraniectomy seem promising to reduce mortality in patients with malignant MCA-infarction. However there is a need of evidence from randomized controlled trials to accurately asses the effect of decompressive hemicraniectomy.To recieve a good functional outcome and an acceptable quality of life there is a need of randomized controlled trial to identify criteria for selection of patients to decompressive surgery. At the time of writing there are at least four ongoing randomized controlled trials.