Retrospective analysis of 15 cases with acute subdural haematoma receiving decompressive hemicraniectomy was carried out in an effort to clarify the beneficial effect and limitation of this operative procedure. The patients in this series were divided into three groups according to postoperative intracranial pressure (ICP). Decompressive hemicraniectomy was effective in lowering ICP in all patients except for the cases that developed acute brain swelling. Overall mortality rate was 66.7% in this series. Preoperative clinical status, and intra- and postoperative ICP and CT findings obtained within 24 hours of operation were correlated with the operative outcome.