Objective To investigate the changes of pH of cerebralspinal fluid (CSFpH) and intracranial pressure(ICP) in the brain tumor patients during nurosurgery, in order to explore the measures for regulating ICP during these procedures Methods Forty-five patients suffering from brain tumor, scheduled for nurosurgery under diazepam-fentanyl-sodium thiopental-atracurium anesthesia, were randomly selected CSFpH and ICP were measured concomitantly during different phases of operation, including pre-anesthetic,post-anethetic periods, tracheal intubation, incision of the durae, excision of tumor and extubationResults As compared with those before anesthesia ,ICP increased gradually and CSFpH decreased gradually after the induction of anesthesia (P