Intracranial pressure (ICP) was continuously monitored in a thirty-two-year-old female of acoustic neurinoma complicated with chronic renal failure. Severe headache with vomiting has begun to appear during hemodialysis for several months, prompting a diagnosis of an obstructive hydrocephalus. Continuous ventricular drainage was placed after admission and changes of ICP were monitored during hemodialysis. Dynamic changes of electrolytes, protein, sugar, urea nitrogen, and creatinine levels in the cerebrospinal fluid (CSF) as well as osmolarity were measured every one hour during the hemodialysis. An increment of ICP started to occur gradually after initiation of hemodialysis reaching the maximum value 23 minutes later. It was spontaneously decreased to the initial level 8 minutes later followed by fluctuations thereafter consisting of the changes of 20 to 30 mmHg. A remarkable rise in osmotic pressure in CSF has been observed corresponding to the rise of ICP which created a large difference from the blood osmotic pressure that consistently decreased following the onset of hemodialysis. Whereas, the absolute values of all measured factors including electrolytes and urea nitrogen in CSF have decreased consistently which did not seem to contribute intermittent increment of osmotic pressure of CSF. The cause of ICP increment in our case was considered mainly due to increase of water content in the brain tissue caused by the widening of osmotic gradient between the CSF and blood, although the substances responsible to the actual increase of CSF osmotic pressure remained unclear.