This chapter reviews basic neurophysiological principles and specific approaches to the management of intracranial pressure (ICP) as they relate to clinical neuroanaesthesia. It also reviews intraoperative management of the patient with a supratentorial mass lesion. There are six interrelated components that are important to the practice of neuroanaesthesia. They are maintenance of cerebral perfusion pressure (CPP), cerebral blood flow (CBF), cerebral blood volume (CBV), intracranial pressure (ICP), CO2 responsiveness (CO2R) and cerebral oxygen metabolism (CMRO2). The common types of neurosurgery can be divided into excision of intracranial mass lesions, especially supratentorial tumours, decompressive procedures in major head trauma and aneurysm clipping. The chapter focuses on managing elevated ICP as this is a problem common to all types of intracranial surgery, and then specifically the management of supratentorial masses. Management of the patient for neurosurgery requires a good understanding of the interrelationships of neurophysiology, pathophysiology and pharmacology.