ICP monitoring per se has never been subjected to a prospective randomized clinical trial (PRCT) to establish its efficacy (or lack thereof) in improving outcome from severe head injury. Hence, there are insufficient data to support its use as a standard. However, there is a large body of published clinical experience that indicates that ICP monitoring (1) helps in the earlier detection of intracranial mass lesions, (2) can limit the indiscriminate use of therapies to control ICP which themselves can be potentially harmful, (3) can reduce ICP by CSF drainage and thus improve cerebral perfusion, (4) helps in determining prognosis, and (5) may improve outcome. ICP monitoring is therefore used by most head injury experts in the United States and is accepted as a relatively low-risk high-yield, modest cost intervention. Comatose head injury patients (GCS 3-8) with abnormal CT scans should undergo ICP monitoring. Comatose patients with normal CT scans have a much lower incidence of intracranial hypertension unless they have two or more of the following features at admission: age over 40, unilateral or bilateral motor posturing, or a systolic blood pressure of less than 90 mm Hg. ICP monitoring in patients with a normal CT scan with two or more of these risk factors is suggested as a guideline. Routine ICP monitoring is not indicated in patients with mild or moderate head injury. However, it may be undertaken in certain conscious patients with traumatic mass lesions at the discretion of the treating physician.