Subtemporal decompression, although seldom used today for the management of hydrocephalus, pseudotumour cerebri, or premature closure of cranial sutures, is still used in many centres to alleviate intracranial hypertension caused by tumour, trauma, or severe intracranial haemorrhage. The charts of 50 patients undergoing subtemporal decompression for either severe head trauma or severe intracranial haemorrhage were reviewed. Preoperative and postoperative computed axial tomographic scans were available in 15 patients for analysis of the effects of decompression on the underlying temporal lobe. Calculation of the additional space provided by subtemporal decompression ranged from 26 to 33 cm3.