Introduction of the transcranial Doppler method 1982 (1) by Aaslid made it possible for the first time to monitor noninvasively the cerebral haemodynamics after severe head injury, or in polytraumatized patients in the emergency room. Mean flow velocities (FVmean) and systolic-diastolic frequency spectrum (PI) in basal cerebral arteries were considered. In that way, influences of different pathological intracerebral processes to cerebral haemodynamics are detectable earlier and triage planning of therapeutic steps is facilitated. The following haemodynamic changes are detectable: Increased intracranial vascular flow resistance due to raised intracranial pressure after SHI, hyperaemia due to short-term hypoxia or SHI, decreased intracerebral perfusion after ischaemia or beginning cerebral circulatory arrest, and increased flow velocities (FV) in case of traumatic A.V. fistulas or traumatic vasospasm. Primary experiences in patients with raised intracranial pressure were collected by Hassler, who found a correlation between characteristic Doppler flow signals in case of increasing intracranial pressure and circulatory arrest (Abb. 1). In case of space-occupying epidural, subdural or intracerebral bleedings or brain swelling, the average FV decreases and the pulsatility index increases as a sign of high flow resistance. In beginning of circulatory arrest, oscillating flow or systolic spikes are detectable. After resuscitation early posthypoxic flow acceleration is also visible immediately after admission to the emergency room. In case of ischaemia with detection of hypo-densities in CCT scan, flow velocities are decreased. Traumatic A.V fistulas, especially the carotid sinus cavernous fistula (CCSF), and the haemodynamic consequences to the circle of Willis are seen, a high mean flow velocity with increased end-diastolic flow at fistula sight being noticeable.2+ in the emergency room. If this is not possible, interpretation of flow signals and measured flow velocities can be only made by comparing both sides. All measurements should be made at normal mean arterial blood pressure. This method enables rapid orientation of intracerebral haemodynamics after SHI and facilitates the decision of what should be done first of all.