A correct assessment of arterial pressure state during subarachnoid haemorrhage (SAH) is one of most critical issue in neurologic intensive care and in neuroanesthesia. It is important to evaluate two different clinical conditions during SAH: before and after aneurysmal clipping or embolization. Before clipping it is mandatory to evaluate a possibility of rebleeding and so it is important to maintain systolic pressure at lower level. Otherwise after clipping it can be useful to maintain systolic pressure at higher level to prevent vasospasm and related ischemia. In this review the Authors examine the pathophysiology of SAH and SAH complications as rebleeding, vasospasm and ischemia. According to international data, they propose pressure parameters appropriated for SAH according to timing of treatment so as to prevent and treat SAH complications.