A retrospective study is presented of all the patients seen in a regional neurosurgical unit during 1985 and 1986 who suffered primary brain injury following severe closed head trauma. Clinical outcome is correlated with the type and extent of the primary brain injury, the appearances of the third ventricle and basal cisterns on computed tomography, and the intracranial pressure, where available. Compression and obliteration of the third ventricle and basal cisterns is shown to have a close correlation with raised intracranial pressure and with a poor prognosis.