In adults, the intracranial compartment is protected by the skull, a rigid structure with a fixed internal volume of 1400 to 1700 mL. Under physiologic conditions, the intracranial contents include (by volume) : brain parenchyma — 80 percent, cerebrospinal fluid — 10 percent and blood — 10 percent. Monroe -Kellie doctrine states that the rise in one of those volumes will cause decrease in other two. Intracranial pressure (ICP) can be elevated in traumatic brain injury, large artery acute ischemic stroke, intracranial hemorrhage, intracranial neoplasms, and diffuse cerebral disorders such as meningitis, encephalitis, and acute hepatic failure. Raised ICP is also known as intracranial hypertension and is defined as a sustained ICP of greater than 20 mm Hg. ICP is normally lower in children than adults, and may be subatmospheric in newborns. It must be emphasized that ICP is not just a number but its long-time dynamic must also be taken into consideration because some specific shapes of pressure waves can indicate pathologic states. The measurement of ICP can be done using invasive and non- invasive methods.Invasive methods of ICP measuring can be undertaken in different intracranial anatomical locations: intraventricular, intraparenchymal, epidural, subdural, and subarachnoidal. Ventriculostomy is considered the gold standard in terms of accurate measurement of pressure, although microtransducers are generally just as accurate. Ventriculostomy has also an advantage of being therapeutic method as well because excess of cerebrospinal fluid causing the raise of ICP can be easily drained. Both invasive techniques are associated with a minor risk of complications such as hemorrhage and infection. Furthermore, zero drift is a problem with selected microtransducers. Newer studies have questioned the benefit of the invasive intracranal pressure measurement.New methods of telemetric wireless measurement techniques are also emerging. Non-invasive methods include transcranial Doppler, tympanic membrane displacement, optic nerve sheath diameter, ocular pressure, near - infrared spectroscopy, CT scan and MRI. Those techniques are without the invasive methods risk of complication, but fail to measure ICP accurately enough to be used as routine alternatives to invasive measurement.