The beneficial effect of decompressive craniectomy in the treatment of head trauma patients is controversial. The aim of our study was to assess the value of unilateral decompressive craniectomy in patients with severe traumatic brain injury. We retrospectively investigated 49 patients who underwent decompressive craniectomy. Intracranial pressure, cerebral perfusion pressure, therapy intensity level, and cranial computed tomographic scan features (midline shift, visibility of ventricles, gyral pattern, and mesencephalic cisterns) were evaluated before and after craniectomy. The gain of intracranial space was calculated from cranial computed tomographic scans. Patient outcome was graded using the Glasgow Outcome Scale. Thirty-one patients (63.3%) underwent rapid surgical decompression within 4.5 +/- 3.8 hours after trauma; in 18 patients (36.7%), delayed surgical decompression was performed 56.2 +/- 57.0 hours after injury. Patients younger than 50 years or patients who underwent rapid surgical decompression had a significantly better outcome than older patients or patients who underwent delayed surgical decompression. Craniectomy significantly decreased midline shift and improved visibility of the mesencephalic cisterns. The state of the mesencephalic cisterns correlated with the distance of the lower border of the craniectomy to the temporal cranial base. Alterations in intracranial pressure, cerebral perfusion pressure, and therapy intensity level were not significant. The overall mortality of the patients corresponded to the reports of the Traumatic Coma Data Bank (1991). Although there was a significant decrease in midline shift after craniectomy, this did not translate into decompressive craniectomy demonstrating a beneficial effect on patient outcome.