Recently the influence of respiratory depression, hypercarbia and hypoxia on the intracranial pressure during general inhalation anesthesia has been strongly stressed. The study was taken to determine quantatively the effect on the cerebrospinal fluid pressure in dogs. 1) CSF pressure was determined during anesthesia via cisternal puncture with direct water-manometer and polygraph recording. 2) The changes in blood pressure, pulse rate and temperature with 0.5% halothane were observed. 8) CSF pressure was apt to rise within 30 minutes with halothane but later It gradually returned to normal or decreased slightly. This was associated with little changes or with slight rise in central venous pressure. 4) This emphasized factors related to good anesthetic technic in neurosurgery. it is recommended that preoxygenation before the induction period should be done in the administration of halothane.