A report of clinical observation was made on the five cases of low cerebrospinal fluid pressure syndrome that we encountered recently. The age of these patients ranged from 27 to 40 years all being female. As for the causative factors of this condition, the puncture of lumbar spinal fluid appeared to be the cause in one case, the trauma of the head in one, but there could be found not any noteworthy cause for the rest of the cases. The subjective symptomes common to all were headache, nausea and vomiting, and the headache was of the nature to be aggravated on assuming the upright posture. Examinations revealed the low pressure of cerebrospinal fluid was the characteristic feature of this syndrome the maximum of which being 60 mmH(2)O. Otherwise, aside from an increase in the cell counts there could be observed no other noticeable abnormality. As for objective and neurological symptomes no other than bilateral extensor plantar responces and stiffness of the neck could be detected. The administration of hypotonic glucose solution into the vein and physiological saline solution into the subarachnoidal space proved to improve their symptomes and the prognosis was favorable in all.